The best advice you are going to get is to buy or borrow a 12 gauge shotgun that can fire 3" magnums and maybe even 3.5" supermagnum shells and then ride on the coat tails of a local experienced and already equipped veteran goose hunter. Surely in Wisconsin there are ample numbers of goose hunters, you just have to locate one or two who will let you tag along. Don't buy a bunch of equipment before trying out the sport and learning more about whether you really like it or not. And as far as a shotgun, you don't have to spend a lot of money to get something that works spendidly. I have been using my Remington 870 synthetic stocked 3.5" 12 gauge shotgun for maybe four years and have found it not a whit inferior to other more expensive 12 gauges out there in terms of reliably functioning and shooting birds. This shotgun cost all of $280 brand new.
After you have been in the sport for awhile and know what you are doing THEN load up on equipment and buy a high dollar shotgun if you want. I have nothing against higher cost shotguns -- in fact I would sort of like to obtain a Remington SP-10 semiautomatic 10 guage shotgun, but paying college tuition for my kids makes that only a fond dream at this point -- but just think you don't need to burden yourself with a high capital investment to get started.
Think about driving out to Denver to take Colorado Luckydog up on his offer!