I can't remember, I've played this game a couple of times, and have a few saves.
In no particular order...
Nissan Skyline GT-R N1 '91.
BMW M3 '04.
BMW M5 '05.
Mitsubishi Lancer Evolution VI GSR TME '00.
Mitsubishi Lancer Evolution VI GSR '99.
Toyota Sprinter Trueno GT-Apex (AE86) '83.
HPA Motorsports Stage II R32 '04 (Absolutely terrible car).
Mazda MX-5 1800 RS (NB, J) '04.
The more expensive cars I purchased using the starter 10,000Cr. & the 100,000Cr. GT3 transfer combined with the winnings used by the cars from the license tests.
Tactically speaking, the MX-5 was a very good first car to start off with, and I'd recommend it if you can afford it, I think it's 23,000Cr. which leaves you with 77,000cr. to tune & customise.
From there you can enter;
Sunday Cup,
FR Challenge,
Spider & Roadster,
NR-A Roadster Cup,
Roadster 4H Endurance - 25%,
And a couple of others I think.