I stopped waiting for a good car because various races have different tiers of cars. If you're joining a game, you have no say. It'd clearly take a while to get one of every vehicle to "legitimately" use in each race category. And this is considering that they separate cars by type, and the only way to really know the type is to know by stealing one before purchasing one online.
u only rly have to buy the top tier cars. everyone should have 1 of every category, i do except i sacrificed compact bc it's so slow and i like my muscle cars. some elite cars u can grab off the road are
muscle: gauntlet
compact: blista (better than the issi)
offroad: injection
sedan (might be coupe idk): schafter or tailgater
suv: baller
bike: akuma
sports: you get a free rh8 for signing up for rockstar social
those are good cars for half of the classes online and u can find them all p easily in freeroam. get a few transmission upgrades or the turbo and you're set. only one play of base invaders to get the turbo