There is a saying in the automotive enthusiast community which states, "The answer is always Miata."
And it's apt, as the Mazda Miata is cheap, sporty, and offers the sort of fun that can be enjoyed by the newest of drivers, all the way to professional racers. It's why it's one of Mazda's most successful offerings, and why anyone with a Miata will talk your ear off until you relent and buy one yourself.
Having driven a number of them, however, I can say they're pretty solid sports cars.
Seemingly the only issue with The Answer is that it's underpowered and doesn't sound all that good. The latter of which is something that not even a nice exhaust can solve. But what happens when you toss a superbike engine between the front wheels? And what happens when you throw a 13,000-rpm screamer into a Miata?