for the plate races you can win with the default gears, bump the tire pressure up to 28 for better top end, set the suspension at 55 on the rear, leave it at 50 on the front, this will help keep the car from sliding once the tires get worn, if this is a little too tight for your liking try 48-49 on the front
you should be able to finish high even if you are just starting your career