I do not really have anything to add, you were given solid advice. I started off upland bird hunting with a 12-gauge Remington Model 870 WingMaster many years ago. I have used my wingmaster to kill everything from Canada geese to doves. The 12-gauge is not too much gun, just match the ammo to the game you are hunting and you will be fine.
I also recommend shooting trap or skeet in the off season.