In a race, you need to own the fastest car and the skills to win it. You can gain skills through constant practice, but that won't allow you to upgrade your car. You need lots of money to upgrade your car to become better than before.
Drive your car as fast as you can till you reach the finish line. In this game, you are going to battle some of the fastest cars in the world and you need to get at least the third spot to be able to unlock the new level. Use the money that got from the race to upgrade your car. You would need that to stay ahead of the game.