If you're buying a shotgun, don't piddle around with 12s or 20s. Go to Cabela's, and pick up the nicest 10 gauge you can find, Remington, Browning, etc. Pumps are nice and more functional, but autos will make the gun a little more user friendly. :lol: I picked up my first 10 last year, and wished I would have purchased one years ago.
If you insist on an affordable, reliable 20 or 12, I prefer the 870. I know some guys swear by Mossbergs, but they always seemed "plasticy" and cheap to me. My 870 was purchased new for $175 about 13 years ago, and even though I have an over/under I like to shoot, the last few years, the only time the O/U gets used is at targets or during deer season. The rest of the time, the 870 is having shells run through it, and its good for every thing from dove/quail to turkeys and geese, with the proper choke.