My personal advice, get every license. as soon as you win like a Skyline or other powerhouse that can sustain over 230mph on the test "curse", go directly to 'like the wind', and get the 787b. The mazda that won the LeMans back in the day, it only has a 5 speed, but some one posted that they won a couple of the formula 1 races with it. It drives blindingly fast, handles extremely well and kicks mucho butto.
Other than that, just keep working those prize cars. I am over %35 and only bought 1 car, the trueno, to get started. I am only using the prize cars so far. If you hit an event that bites, skip on ahead, win something very nice and come back...