Reached Driver Level 50.
You'll need a total of 8,000,000 XP in order to reach level 50 (which is isn't hard in this game). You'll get it while attempting to achieve gold medals in all the challenges.

But if you under any circumstances want to level up early, here's a method I found that will net you around 53,000+ PTS, within less than 30 seconds.
Play the first challenge (Rio Speed Check), then pick Dodge Daytona 1969 and these mods Double Acceleration - Top Speed - Super Boost.
You'll need to aim for the gold medal each time, because it nets you 50,000 PTS. (there are 2 cameras in this challenge and you need a total of 260.00 MPH speed to get gold medal).

Tip: DON'T use your N20 tank at the first camera, instead, use it at the second camera (last camera). When the challenge ends, you'll have more than enough for the gold medal. Now keep spamming the button until the race restarts. Rinse and repeat.