I used to shoot alot of trap back in the day, I have my ATA 25, 50 and 100 pins somewhere. I'll just jump on the advice of most other people here. Pattern that gun, see where it shoots. Get some lessons and improve your shooting. The three disciplines are quite different in targeting, and I haven't spent much time with skeet or sporting clays, but what shooting I have done has let me know how different they can be.
I used to shoot with a guy who was one of the top american shooters, I believe he had won the Grand American one year or few. Anyways, sometimes when someone would blame their gun, or choke or anything, he would put down his dt-10 and offer to try out their old beat up 870, and after a couple of shots, he would smash the targets with it, and shoot 18+ with ease. It's really about the skills and not the equipment.
In terms of tram, figure out what kind of shooter you are, and go from that. It took me probably more than 100 rounds to figure this out. I end up waiting on the target a bit to hit it's peak height, then shoot. For my style a full or extra full was what worked best for me. I found I didn't reliably hit them at the longer ranges, or when shooting handicap with an IC, and mod/IM would chip targets but I loved inkballing them.
One thing to think about in ... not being great hitting targets is if you have a flinch, a good coach should help to determine this, and if its from the gun, or the target.