See if you have a IDPA or a USPSA chapter in your area.
You can read up about them here.....
If you have a match close, even if you don't want to shoot it.....yet, go and watch and talk to some of the shooters. For the most part, everyone associated with the sport will be more than happy to talk to you about it.
Before you spend the $$$ on 3 guns, you might want to try shooting competition with one gun to see if you like competition shooting. Along the way you can get an idea of what kind of guns you might want to get for 3-gun. Make sure you talk to a few different people, everyone has their favorite firearms, and what is good for them, might not fit you.