Coins
Ignore the coins and just focus on keeping your vehicle from colliding with walls. You will earn a new car every few hours, making coins less important. Only get coins when it is safe to do so. Coins are also awarded for completing missions.
Control
Use small brief motions to continue your drift. Adding too much spin to your drift will send your vehicle in a constant swerve. Remove your finger from the screen and your vehicle will slowly straighten out. This may help if you are out of control in the middle of a series of turns. If you can reset your vehicle's orientation, you may be able to regain drift control. The level layout is static. Memorize the track and try to do better with each subsequent run.