Just have patience around lapped traffic, sneak past them then go very deep into the next corner so they don't have a chance at bumping you. Oval rookie is full of wreckers, just because anybody can sign up for a 6 month free account, so you just have to avoid them like the plague. If it means not winning the races, who cares. Your only goal in Rookie is to get out of Rookie, then you start worrying about winning.