Yeah like the other guy said, if someone invites you to go goose hunting, most likely they will have everything, but your gun and your steel loads! 3 1/2 mags. are in my opinion the best for geese in BB shot! There are many brands that range in price!
If i were you i would get the Power clucker goose call From Zinks calls! you can get it with an instructional DVD for 30.bucks and its a great easy blowin call for beginners! If your on the market for a new gun and dont wanna spend alot of money, then i would go with the Benelli Nova Pump! Averages around 439.00 new and is a great shooting durable gun!
If your buddy doesnt have a layout blind, then i would look into that too! Some good camo in Advantage Max 4 HD would be a good idea too! Decoys are expensive and your buddy probably already has those! A goose flag is nice to have, to entice those birds from far away! but use it sparengly or they will bust and go away! I hope this Helps you and if you need anymore info just let me know,
Thanks,
Team Fowlplayaz!
And good luck, I dare you not to get HOOKED!