OK, once you get up to around Level 10, you'll have a decent enough car (I had a 69 Fairlady tuned to a P.I. of >900). This'll be more than enough. Turn all the diff. mods to maximum, then pick the first track in the Proving Grounds Japanese Series. It's a very easy track (2 laps of what's really a slightly more complex rectangle). Even if you don't race at speed (you only need to do the straights in third gear and the main corners in second), as long as you don't make any huge errors and drive off the track, you should beat them by a fair margin, as they're all C/D rated.