The first section in career is labeled Proving Grounds. There are 30 total races in proving grounds. You must earn a gold trophy on each race. If you are new at the game, I suggest you race on easy. If other race series open up, such as: semi-pro, amateur, manufacturer, etc.; Play them to unlock some higher level cars, then go back and play proving grounds. The higher level cars and increased cash from playing harder races, will allow you to blow through the Proving Grounds races (which are the easiest and shortest races in career).