Hi there, so I platinumed GTAV a while ago and I ranked them based on difficulty, how long they took, and just generally how fun they were to achieve. This also is kind of a walkthrough of some sorts and includes tips for some of the more difficult ones. Oh and keep in mind that this is just my opinion, some trophies can be achieved easier by other people.
And there is some swearing in this, but that shouldn't be a concern considering this is talking about GTAV Pick option C at the end of the game so you don't miss any achievements

1. Pimp my sidearm- works on any gun, recommend beating the game and then fully mod a pistol for the cheapest results.
   
2. Los santos customs- beat the game and take franklins car (trust me, do franklin's car) and go to a Los Santos customs and buy every option
   
3. A lot of cheddar- When you finish the game go to one of the stock websites and purchase every stock you can, which means you should be able to purchase 40 million worth of stocks at a time, do this until you unlock the achievement. This should take around 2 minutes.
   
4. Out of your depth- Purchase a boat or call a taxi (if you do the taxi achievement before this one the taxi skips are free) and go to the ocean, drive or swim to the very end and swim down to find a shark, annoy the shark so he will kill you. Depending on how you do it should only take around 5-15 minutes.
   
5. Off the plane- nothing needed to be said here, just complete it.
   
6. Clean sweep- Just stay behind cover and purchase snacks and body armor, and use a gun like a pump shotgun or a one-shot weapon, such as the revolver.
   
7. Trading pure alpha- you can do this anytime within the game, just purchase a stock and then kill yourself repeatedly until next to your stocks a green arrow pointing up appears, sell it and you should get the achievement. Can take up to 5 minutes if stock prices don't go up quickly.
   
8. Three-man army- Play as franklin and call Micheal and Trevor and pick them up, get a wanted level and stay in your car, kill a cop so you can get 3 stars, and start driving away but still have the cops on your ass. Do this for 3 minutes and you should get the achievement easily. Make sure your car has some armor upgrades though.
   
9. Alls fare in love and war- After beating the mission Mr.Philips you are able to purchase businesses when you're able to play as franklin purchase the taxi business for 200k and then you should get a call after a while, do the job and you should get the achievement. The missions themselves don't take a long time, maybe around 5-10 minutes, if you don't get the achievement to try to do another one.
   
10. Red mist- After completing the Trevor Philips industries mission this will just look like standard strangers and freaks, complete it, and then the others should pop up after you finish the one before. Complete all 5 and you should get the achievement. Can take up to 30 minutes to an hour if you're not good at it, I recommend trying to get the gold for all these for another achievement.
    
11. Altruist acolyte- There are certain markers that will appear as you get close to them, play as Trevor and go to the "Domestic" random event, there are a few closer to the location such as the hitch lifts but I wasn't able to spawn them. Drive to the cult and you should get the achievement after the cutscene. Took me around 10 minutes if you use the domestic random event.
    
12. Wanted: Dead or alive: This will also appear as Trevor strangers and freaks, after doing it you will get an email giving a picture of where he should be hidden, you can search it up on youtube as I did and capture him, don't kill the target no matter what, deliver him to Maude and you should unlock the achievement. Took around 10 minutes.
    
13. Kifflom! Play as Micheal and go to the Epsilon Program website, and pay the 1000 dollars to start this, I recommend using another guide for this but whenever you need to do something like wear the robe for 5 days just go to Michael's house and sleep until you are able to go on another mission, and when you need to walk around the desert for 5 miles just walk in a circle. this can take up to 3 hours if not done correctly.
    
14. San Andreas sightseer- Purchase a helicopter for the quickest results but can be done using a car or a boat. Travel around and get 95% of the map uncovered, you can tell if it's uncovered by it being transparent, meaning you can see through the map. The reason why I recommend a helicopter is you also need to uncover the ocean as well, which can be done with a boat but the helicopter is faster, you can either steal one or purchase a helicopter hangar and a helicopter. Took around 5 minutes because I already had a lot of the map uncovered.
    
15. Multi-disciplined- You'll need to get a single gold in only one of the shooting range challenges, triathlon, a flight school lesson, a sea race, a street race (which only franklin can do), and an off-road race. Complete all of them anyway for 100% achievement. This can take up to 30 minutes to an hour if you aren't able to gold one.
    
16. TP Industries arm race- After beating the mission Mr.Philips you need to purchase the hangar after beating the mission, it should cost 100,000 dollars. You get a special marker for the dune buggy and the airplane, there are 10 in total, 5 for the dune buggy (which is mainly just collecting supplies) and another 5 for the airplane (which is also mainly just supply drops) After doing the two quick save your game and reload it for the two missions to spawn. Can take up to an hour if doing the quick save method.
    
17. Crew cut- To easily finish this you either need to make a crew for a friend to join or join a friends crew
    

and play a contact mission with them to get the achievement.

1. A new perspective- Just leave one of the characters in the first person and just wait for the 15 hours or play some of

the story in the first person, I just recommend leaving it on overnight.

1. Calling digits- reach rank 20 and have 5000 dollars, call up Merryweather and ask for a backup helicopter.

20- stick up kid- rob every store on the map, can take up to an hour depending on how fast you move to each store.
21- enjoy your stay- for this achievement you need to play golf, play tennis, play darts, arm-wrestle,
win a shooting range challenge, rob a store, buy a lap dance, buy any clothes, buy a tattoo and change your hairstyle. Make sure you win or lose the sports activities because if your teammate leaves in the middle of the match it won't count.

1. Three-bit gangster- Pretty simple since ranking up is easy, just play 3x or 2x events or contact missions for the best RP. Can take up to an hour or two.
   
2. American dream- You're most likely going to need at least 1,000,000 dollars for everything, grind the 3x or 2x event or play heists for money.
   
3. 4-bit gangster- Same as a Three-bit gangster but more grinding is required. Can take up to 5 hours of pure grind.
   
4. Full refund- After rank 50 have a friend call Lamar so he can call a thief on you, kill the thief and take back your money. Takes around 5 minutes.
   
5. The midnight club- You can have a friend let you win 5 races by going to the menu-jobs-races and then
   

invite your friend and have you win 5 with a custom vehicle, depending on the map you play on
(I recommend taxiing, takes around 2 minutes to complete it) this can take up to 10-30 minutes.

1. Backseat driver- Do this with a friend, wait for people to join or join a rally race, and then guide them through the map. Once again I recommend making the rally race so you can play on a map you are familiar with.
   
2. Run like the wind- I did this in a solo match, I stole a car, got a bounty, and survived a GTA day (which is around 48 minutes) Move around and don't get kicked, you can die by anything but another player. You can do this with a friend where they have Lester give you a bounty.
   
3. Show off- Use an upgraded vehicle (preferably franklin's personal car) and search up a guide for all locations, ill put a link to the guide I used in the description, while most are easy 10 of them are a complete bitch, and took me around 15 minutes just to do one of them because of the requirements. This can take up to 3-5 hours.
   
4. From beyond the stars/a mystery solved- I can't really decide on which one is harder so I will group them up into one, both took me around 3 hours to do since there are so many. You can use the rockstar social club website or use a guide on YouTube as I did.
   
5. Waste management- After the second heist Micheal or Trevor and purchase the old dock for around 250,000 dollars, while it can be confusing just follow the dot on the map. Took me around 2 hours to do.
   
6. Close shave- Look up a guide, it's pretty much required for this. Buy the buzzard helicopter for the under the bridge and keep in mind not to do too much damage to your helicopter or it won't count, while most recommend stealing a jet from fort zancuddo I instead bought the mallard for 250,000. Took me around 3-4 hours.
   
7. Decorated- In GTA online there are certain rewards for doing certain things such as killing people with a pistol a certain amount of times, every single platinum that I earned were headshot kills, sniper kills (not sure how to be honest) Kill people using melee weapons, kill people using sticky grenades, kill players in GTA online, kill psycho's (I recommend doing most of these in deathmatches) win 10 waves of survival, (it's painful and achievement on its own), rob 20 stores which is also an achievement, pay for 25 lap dances (all you need to do is pay for the dance and then exit it) buy 25 haircuts, have a friend drive you around for a few hours (sit in a car with your friend in it, pretty simple one) Flippin hell (go to a stunt race with a flying car, get high in the air and do the flips) steal vehicles (pretty simple) Achieve the fastest lap in a race (can be done with a friend) land jumps 300 feet in a road vehicles win every deathmatch and race mode (can be done with a friend) participate in 25 races, buy 25 pieces of clothes (just buy 25 shirts) get the most kills in a 4 player survival (not too hard unless you camp all game, can be done with a friend) get the most kills in a gang attack (also can be done with a friend) shoot cop choppers down (when you get 3 stars start shooting the choppers down with a homing missile) win every race mode at least once (needed for 2 achievements) get a tattoo on every body part, win a race in a custom vehicle (needed for achievement anyways) wheelie for over 2000 feet (I don't remember getting this one, but the best way is to do it at the airport) Activate a 2 person key switch (I did this on the diamond casino heist) Complete the fleeca heist finale, do the aggressive approach on the diamond casino heist and earn 1,000,000 dollars and use the elevator on the diamond casino heist.
   
8. Solid gold, baby!- Do the heist setups and the strangers and freaks, every mission and strangers and freaks I got a gold in (not including prologue) was
   

Franklin and Lamar, Complications, Fatheson, marriage counseling, friend request, chop, the long stretch, daddy's little girl, the good husband, carbon rifles, Mr.Philips, Trevor Philips industries, Deadman walking, did somebody say yoga, by the book, Tow truck, boiler suits, masks, The multitarget assassination, Mr.Richards, Hang ten, Fresh meat, The ballad of Rocco, reuniting the family, Architects plans, doting dad, fire truck, meltdown, stingers, every gauntlet, something sensible, the times come, every Pulling favors, every rampage, shift work, Grassroots Micheal, grassroots the drag, Paparazzo, paparazzo the sex tape, Paparazzo the highness, every vinewood souvenirs expect Al Di Napoli, Exercising demons-franklin, liquidy risk, minute man blues, exercising demons Micheal and Trevor, targeted risk, uncalculated risk, a starlet in vinewood, chasing the truth, the last one, delivering the truth.
I may have missed a few but those were the ones I counted, this can take up to 5-10 hours unless if you already have quite a few on gold. You don't have to do every single challenge at once, so you can try to beat the level as fast a possible, reload it and try to get as many headshots as required for example.

1. Career criminal- This one requires pure fucking grind, let me tell you everything I did for the 100% completion. for hobbies and pastimes, I did Stunt plane time trials, 3 medals in every shooting range challenge, won every race (meaning offroad, street, and sea,) won every sport, got par or under in golf (getting par or under is required,) Bail bonds quarry and farm, every flight school mission, every arms traffic race (required for an achievement anyways,) got a private strip club dance, hunting, yoga and parachuting. Only franklin's strangers and freaks are required, my random events were the ATM robbery, Bike theft 1, construction accident, gang imitation, mugging 1, 2, and 3, security van 3, 4, and 6, sportbike theft, a countryside gang fight, a deal went wrong, and the drunk driver. To find out the spawn points of the random events go to the rockstar social club. All 30 misc were buying a haircut, weapon, any clothing, a car mod, a tattoo, and 5 properties, a vehicle from a website, ride the cable car, use the car wash, go on the rollercoaster, friend activities (meaning call up Micheal, Trevor, or franklin as any of the 3 characters) Visit the cinema, bar, play tennis, darts, golf, go to a strip club, 25 stunt jumps, 8 knife flights, rob a store, purchase stocks, watch T.V. (do at Micheals) complete a booty call (Play as Trevor in a strip club and get one of the girls like the bar to the max and drive them to their apartment) 25 under the bridge, walk and play fetch with chop, get 30 submarine pieces (one of Micheal's strangers and freaks) 30 nuclear waste (it's an achievement anyway) get all 50 spaceship parts and letter scraps (both achievements.) This can take up to 10-20 hours, it's a fucking pain.
   
2. Unnatural selection- Holy shit, this took me so fucking long to do, me and 2 other friends grinded for 10 hours straight and couldn't even beat it. Buy max snacks and body armor and the best map to do is the nuclear silo,
   

there is a certain hiding spot near the stairs and the stairwell that if you hide behind it's super difficult to get shot unless you peak for too long. Use the combat MG, does a lot of damage and can shred through enemy health, be careful at the beginning when getting health and armor not to be out for too long for else you will lose all your health and maybe even die. This took me prolly around 10-30 hours to complete.

1. Above the law- This requires so much god damn grinding that I grinded for 3 days straight, I started grinding hard on level 67 and got to level 100 by doing the 3x event "Target assault race" But by the 3rd day, it was this stupid deathmatch where if you die you can come back to life by an enemy dying or some shit, heists are also good ways of gaining RP, and heist setups too. this took me around 10-20 hours to complete starting from rank 67.
   
2. Numero Uno, the requirements for this achievement is to win a single Bike, Land, Sea, Air, Rally, and GTA-Race, win a Deathmatch, Team-DM, Gang-Attack, and Survival (10 rounds), and win Arm Wrestling, Darts, Parachuting, Golf, Tennis and Shooting Range. So not only do you need to complete the survival bullshit but more on top of it, now everything but a rally race, team deathmatch, and survival you can boost with a friend. But even then this still took me around 10-40 hours to complete due to the fucking survival bullshit.
   

I have written this for people who are starting with 0 GTA$ and making their way into gta online.
So if you don't have a high end apartment, a bunker, a clubhouse or anything like that this method will make you earn a good amount of money to start buying some important things in gta online.
First of all, the most important thing is that forget investing money into a good looking house or a good looking car. You don't need those right now.

Before you read:-

These methods have been tested by me and I now have 5,000,000 GTA$ in my maze bank account right now. However, it takes time. A lot of time. It may even take a month for you to reach this million dollar mark. However, this early hard work can pay off really well in future. And you soon might be making 100,000 GTA$ every day.

Before you start making money, do this:-

An easy way to make your gta online experience better is by playing solo. You can either play solo session or a private public session. The solo session is the easiest way but later it might have restrictions. A private public session can be achieved by tweaking some settings which are different for pc and console. Invite only session can also be considered as an alternate for solo session.
A public lobby may have hackers which can ruin your early experience of the game. Public session may even have high level players that can cause chaos or can try to kill you. I had some difficulties trying to play gta online for the first time with players killing me in a public lobby.

More is better:-

Before you start making money, it is always great to have a friend. It is not necessary but is always better. If you have a friend, you both can play in an invite only session and can play missions together (you both will earn the same).
Also, some missions may require minimum of 2 players. So depending on a stranger may be difficult due to no communication. So if you have a friend playing with you, it is always great.

Starters:-

A vehicle:-
Something wrong many new players do is that they try to invest money in more vehicles. I see people who show off their garage full of cars but didn't spend any money of profitable businesses. You need to know that buying more vehicles is not going to earn money. You just need 1 fast car, and you are ok to get started.
So you need a 'fast' car. For new players, the Elegy RH8 works super great. It is faster than most other cars and is ABSOLUTELY FREE.
To get this free car, just link your social club account with gta online and you have the car.
Alternate method:-
If you don't have a social club account or you don't want to link it. You can just find a decent car in the game and steal it. From there, just go to Los Santos Customs and make it yours by paying some money.
You can store it in your garage anytime.
But make sure the car you choose is fast. These cars are not that fast but will for a new player these are great
A garage:-
Where will you store you car? A garage. When you have just 1 car, you don't need to buy a 10 car garage or a 6 car garage. You just need a 2 car garage that is available on the Dynasty8 website for 25,000 GTA$.
Now if you don't have that money, don't worry. Just keep reading and you'll get that money soon.

Early money:-

Contact missions:-
These are one of the most easy way is to contact characters to earn money.
Basically, characters such as Lamar, Lester, Gerald, etc. will give you missions and tasks which you have to complete and you will be payed for each mission. Some missions may be easy whereas some may be difficult. Again, if you have a friend playing with you, missions can be completed faster and much easily.
Some characters may get unlocked later on in the game but I got my first 100,000 GTA$ by doing Lamar missions. Then you can do some Gerald, Lester, Trevor, etc. missions.
The maximum pay each mission gives is around 16000 - 19000 GTA$ when done at hard difficulty with no mistakes. To based on calculations, by doing 10 such missions, you get 160000 GTA$ minimum that is super great. And there are more than 60 such missions all over gta online.
And if you keep doing other contact missions, you will soon get enough money to buy a decent high end apartment.
Treasure hunt:-
Treasure hunt is the easiest way to earn 200000 - 250000 GTA$. But these are pretty time consuming and tricky. You will get a treasure hunt email at any random time and by collecting all clues, you will be given a revolver. Then do a special task with that particular revolver, and you will earn 200000 - 250000 GTA$ depending upon the task.
The task may be like 'get 50 headshots with the revolver'.
There are walkthroughs of each treasure hunt available. Just google them or search them on youtube.
There are many treasure hunts available but they don't come very fast. You'll have to wait for the email to come and then start the treasure hunt.
Doing all treasure hunts can give you minimum of 500000 GTA$. However, they can take a lot of time.
Spin the lucky wheel everyday:-
The casino has a lucky wheel. And you can get many things from it. You can win a car, clothing or casino chips. You can rotate the wheel once per day.
It is super great if you are lucky enough. The highest prize is a car.
Then comes 50000 or 25000 chips. If you get chips you can either use them in casino games, or you can convert it into money.
Which means, 1 chip = 1 GTA$ and 50000 chips = 50000 GTA$
You also get 1000 chips once every day for free.
Flight school:-
There is a flight school in the Los Santos international airport. There are challenges you have to do in an airplane. Do all of them and complete them at gold medal.
This will give you 240000 GTA$.
Plus, it's free and you will improve your flying skills

When do you earn a million ?

It will take time and skill. There are many ways you earn a million. And they take time and investment. So here are the 2 easiest ways to earn a million that take less investment.
Facility:-
Once you have around 650000 GTA$ you can buy a facility from the maze Bank foreclosures website. The cheapest one is available for 650000 GTA$. From there you can start doing the Doomsday heist and unlock other heists as well. There are 3 acts which you have to do.
The problem ?
It requires investment and friends (not really).
So each heist requires the leader to invest into equipments. You may even need to spend more than 70000 GTA$ for each heist setup. You may even need a good fast and armoured car for better heist.
Then each heist requires 4 people. It is not necessary these 3 people are your friends. You can invite other players in the session to the heist. But many times those people can mess up or you may not even find any person to join the heist.
After all heists, I bet you may be a millionaire or close.
High end apartment:-
This is pretty easy. The cheapest high end apartment is less than 500000 GTA$. Probably 300000 GTA$. Just buy a high end apartment (Weazel plaza, Richards magestic or 3 Alta st.) and you can unlock the heist room. From there you can do heists such as Fleeca job or Pacific job and earn good money.
Again, you need 3 more people.
Positive point, the investment here is lesser than the facility but the pay is also less.

That's it.

After this, you are no longer a beginner

and you can go ahead and buy a bunker or an office. Then become a CEO/VIP and unlock new missions.
If you think i missed something, comment down.
I hope it helped.

Edits:-

u/leekshooter suggested not to do Doomsday Heist for a new player as it may be difficult. You may not have sufficient equipments for the heist when doing Act 3. So make sure you consider the difficulty level if you are new to heists.
Make sure to read the comment of u/braggs0815 as they have suggested a profitable method of earning money with vip jobs and later in the game investing on facility.