What do you want to do? Win?
Start the game with any car.
Earn 20,000.
Complete the Race Wars gold challenge that unlocks the Nissan 240SX. It costs 20,000.
Buy the Nissan 240SX and sell your first car.
Win all the frist three sets of races, get the boss pink slips.
Use the boss cars to win all the Silverton races. I couldn't beat the Murcielago canyon at this stage, but everything else was won.
Buy a Dodge Viper, put all the race upgrades on it. You can even paint it if you want.
Pass the Murcielago on the first sweeping left-hander, and stay in front through the next corner, and you wrap up all except the very last boss race.
This has to be raced with the Viper (Corvette also works, maybe a bit better), and the last Canyon race is the toughest. You have to make a clean pass down Darius's inside on the first hairpin. You have to hold the lead (very, very very tough if you didn't get the first corner absolutely spot-on) through the next turn and you've got the game beat.
There's something about a Dodge Charging behind you at about a hundred miles faster than you, and you still managing to win. Takes something real special, but the 240SX is the only car that can take it without you having to slap any upgrades on it at all.