First suggestion is make your first run or two of the day relatively slow, learn the course and figure out the line you want to take. Once you don't have to hesitate because you don't know where to go, then push it a little more. Most people that go to autocross a lot don't look down on guys that are not fast, but they get sick of guys that go out, get lost and knock down all the cones because they slide all over the place. Don't run out and buy parts right away, the car will not be what limits your times for a long time. This past year a kid in a Prius with Hankook summer tires beat a guy in a BMW M3 pretty bad, just because the M3 is that guy that gets lost for his first 6 runs of the day and won't listen to instructors. Have fun, autocross is a great time.