Get a viper!!
I suggest starting out with a pt cruiser (I know it's ugly, but oh well). Once you start earning some $ you can tune it up some. I know it's tempting but don't buy a $40,000 or so car just because you have the money.
Save until you have about $80,000 and go buy a dodge viper gts. This baby is nice enough stock, and you wont believe how much it can be upgraded. My viper has 1000+ horsepower and it can school the most expensive cars in the game, like a panoz esperante and a mazda 787b. And the best part is that I've only invested about $200k including the original purchase. Trust me on this one, the viper is definitely the best value in the game, and mine can go 270 mph.
More tricks, tips and cheats for this game are right here - Gran Turismo 3: A-Spec cheats
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