As for the tubes, put 'em on paper. You'll probably find that you like F or M for trap, and the IC for skeet. This is a great way to find out if the gun really fits you, too (hit where you point). If you get into skeet, consider getting a skeet choke. I shoot O/U with skeet and IC and like that combo.
As for the ammo, I have gone through about 5000 Challengers with only ONE ftf. I use #8's, and use them for both games (keep it simple). I never buy anything that starts with a W, but that's just me.
Don't get caught up in the choke tube game... it's BS. Find a spread you like, and stick with it. IF we were talking about Sporting clays, I would give slightly different advice, but for trap and skeet, just get out there and SHOOT!!! Have fun... C.