One you get used to Minolta's handling you-ll be winning races easily. Shouldn't take to long to master regardless of skill.
The easiest of the group c cars to handle in my opinion are is the prototype nissans. Using a dualshock 3 they feel like they-re glued to the road.
Below 700 performance points you'll want the Audi R8 Race '01, the non-premium one.
If you want premium(Audi) then buy the premium version; drives slighty less as good.
As for a premium prototype the 787B Mazda is one not many people regret. Great engine noise , cockpit view, handling... its all there.
EDIT: The R89c and R92CP are the Nissans.