To progress further, perform as many tricks as possible to earn boost. Tricks are done by holding or tapping. Both types of tricks will reward you with boost. If your current car does not jump well, concentrate on the tapping tricks. Getting big air and having perfect landings will also result in boost. You will have some control while landing after a jump. Swipe down when your vehicle is in a good position to land to earn boost.
Each car is has a rating, with 5 stars indicating the most rare and best performing vehicle. Sell unneeded cars to get extra money to spend improving your best vehicles. Fuse together the same type of car is also a good way to improve them.