RE: getting started
although I shoot 3.5's I will tell you, from a pump shotgun do not worry about it...shoot the 3" loads.... I believe the 3.5's do offer some advantage, but that is only if you can bear the recoil, and from a pump gun it is simply too much abuse for the benefit.... in a smooth shooting auto it isn't so bad, but a fixed breech gun (pump, O/U, etc) no way....
number 2's or 3's should be fine for most of your hunting...and get a little practiceshooting claysand you'll find you don't shoot nearly as much as the average guy....