If you haven't got one already, I strongly recommend you acquire the Ferrari Dino ASAP.
Primarily because the tyres it comes with suit the car so well. No idea if GT6's Sports Hards are the equivalent to what the real car came with, but they do help make the Dino pretty approachable and forgiving when on the limit, which in turn makes it a fairly n00b friendly way of learning the quirks of the seemingly complex art of MR car control in the game.
But, yeah, it's a hoot and (at 90K Credits) a bargain if you're looking for something cheap to thrash about, powerslide and generally muck about purely for the LOLs.