Buy a car you actually want to "perform" or race with.. and actually race it. Make it separate from the car you drive every day.
Other than that, it's a matter of preference. I have friends who race their Miatas or WRX and have the most fun in the world. I know people who race Ferraris and Porsches and they do have the same amount of fun.
That's great advice !
Don't race a Porsche unless you want to spend 10x what the cost of the car is to do so.
Most of my racing buddies stuck with Hondas and miatas as you can do the same racing but that 10x rule starting with a 5k crapbox is much easier to swallow for most people.
Also: never, ever skimp on the cage, seat, and driver's safety gear. Never.
