I bought the same 1rst car I bought in GT2 and GT3. The used Red 1995 RX7 type R ($13,000). With 100,000 clams from GT3, I lightened it, suspension, added ponies. Its fast.
The car I think I should have bought is the Porsche Boxster (RUF) The mid engine and larger engine should be able to win a few races to upgrade. The mid engine has tackles the turns sticking while all for are skidding. You can learn to rail on this ride. I think it was $80k, which leaves 30k for toys.
My second car was the HPI VW (tuner). for $30,000 it had more of everything for less cash.
Otherwise, I saw style points. Buy what you want. I buy cars only by thier power/weight ratio. Light& fast. After I win a few races, I like the 1960's classic little light euro stuff. I wish they had a VW Scirocco in this game, the real ones are FUN to drive with a few upgrades. A 2004 Black Honda CBR1000rr would be nice too, but not with a steering wheel.
To kids under 18 to reply to me: my name is oYo
for adults that are currently alt+tab'ing between GT4 and "teen pics", its nice tits.
I got GT4 at 89% done 80% wins. lots of golds. Wrecked my bike last week, knee hurt, just getting migraines playing GT4 till sunrise.