The most important thing is fresh brake fluid and high temperature brake pads. You already bought wheels and tires which is good but for the first event I would run the car complete stock. Because you already have the tires on the second event run with the competition tires. As your skills progresses you keep upgrading so that you will feel the progress on your car.
Keep Changing your brake fluid frequently. Change your engine oil at least half way before BMW give you the free oil change.
Ohh Don't forget to have fun. Don't worry if other people on 330Ci or "slower" cars are passing you.