Greetings XDMFAN, and welcome aboard.
With respect to a shotgun purchase, first you need to establish if you are going to be using slugs or buck-shot. Not withstanding local regulations, if your anticipated shooting environment will be close shots (presumable in heavy cover) then just about any 12-ga will successfully deliver a load of buck-shot. As the environment opens, and the shots are longer, then the slug specific guns come into favor. For maximum shotgun range, many select a rifled barrel with scope and sabot-type slugs. A great feature of the modern pump and semi-auto shotguns is changeable barrels. You can use the same gun for birds and bucks. Your best advice can often be had from the locals where you intend to hunt.