Maybe the Skyline or the Camaro race car. I made a lot of headway at this point of the game with these.
Really at That point I won as many series and specialty cars as I could. I say the Skyline and Camaro, but it's not like these were the only cars I used fom 15 - 75%
You don't need to worry about buying the one car that will do it all for you. If you can win the Beginer Championship, or the American or European champs in amatuer you will not need to buy a car until you feel like running the Mercedes or Alteeza races or something like that.