As for what type of competition you should research, well that completely is in your hands, but if you are interested in 3 gun, that's a greats place to start. Tons of info out there on 3 gun if you search the web.
As for equipment in most sports, you pay to play. hard to say whether you can be competitive with an sks as it depends on your individual skills, but I doubt many top competitors would use them over the AR.
You have to start somewhere and it's good to see the interest in getting involved