This is hands down the best and fastest way to level up in GTA Online. It is so easy and simple as well!
All you have to do is host a race called 'Criminal Records'. It is a round circuit around the prison. In the race settings, set it to 2-3 laps, make sure wanted levels and traffic are on and set the split times option to
personal. You will need 2-4 people and you can set the car class to anything you want but you can finish the race faster using super.
Start the race and just drive around the track, once you finish the first lap your RP bar should come up at the top of the screen and you should earn about 3000RP if you did it right. You will get slightly less for the next laps but still a lot. When the race is done, the leaderboards will show that you have only earned about 1000RP but you have actually got a lot more. You can just repeat the race over and over to earn even more RP and level up extremely fast.
This is also a good way to increase your racing skill if you haven't maxed it out already and it is good to get wins to unlock tuning upgrades for certain cars.
