Your 2 3/4" shotgun will do just fine, i have been shooting geese for 9 years now and i have yet to use a 3 1/2" shell. I would go with 1 or 2 shot so that will give you a few more pellets. As far as buying decoys i would talk to your buddy to see what he thinks about it and wait to see if it is a sport that you want to get into. You also might want to look into some waterfowl type camo.