Additional cars will become available through natural progression as you win more races. Usually by level 15, you should have three cars to choose from. Collect from the premium crates that are given free every two days and the regular crates. Win stages to have a chance of winning car cards. Tap any car desired and complete the stages or requirements that are listed. You can also spend in-game currency on the Black Market to get blueprints. Complete a Special Event to get a reward that may be a new free car. When your car collides with other cars or obstacles, it will become damaged. However, besides losing some time and speed, the damage will not be permanent. You will not have to repair your car or spend money to get it back on track.