Have you done much track driving? Are you at a level where you could go to a new track, be relatively competitive and not a danger to the other drivers? If relatively inexperienced, then track days are the ideal start.
Im at the track days level and really enjoy it. Depending on the car you choose, even that can be expensive!! The GTR is just silly on tyres and brakes, hence why I moved to the MX5.
A good friend of mine does sprinting, but has not been having good luck with his car over the last few years.... 3 gearbox builds, 3 engine builds and now a 2nd head build. Not to mention, new FIA seats, suit, new turbo and the list really does go on.
I have always want to try RallyCross, looks like great fun, but the car that you use must be trailered as there is the potential for damage. So you need a tow vehicle as well.
It is not a cheap sport!!! Painful some days....