Go to the bank, Make a savings account, earn interest.
naw, j/k. Just keep on racin' and save your money until u can buy a really good car. Or mod out a car u have now.
Wait... the GTO isn't really one on of the best handling cars in GT2 b/c of its weight. In real life it has all wheel steering to fix this, but not in GT2. Anyway, either car is a good choice.