Number 1 thing is scouting, be where the birds want to be, they are in that field for a reason and 99% of the time it is food, if you are set up where they want to be it sure makes life alot easier.
Number 2 is your hide, be it an A-frame, layout, natural fence line or "other", blend in well and don't move when they are close. When in doubt, add more natural camo material.
Number 3 is decoys, just starting out grab 5 dozen silhouettes, Big Als, dive bomb, real geese that should do fine for starting out. Remember, if you are on the X you are just trying to get them feet down in front of you. If you like the sport, then you can go in the poor house buying decoys.
Number 4 is calls, no need to get the newest custom acrylic $200 call, plenty of cheap poly carb call that can get you started. Like said above, poor calling is worse than no calling, so practice alot.
Number 5 is everything else, I always have a flag with me in a field, some days I would give up my calls for the flag. Guns and ammo, any 12 ga with either 1, 2 or BB steel shot in a mod choke will kill any goose on the planet inside of 40 yards. You don't need a 3.5" gun or TSS shot, know your range, they are alot bigger than you think and can look close at 60 or 70 yards.
If you like the sport, which you will, then you can start playing around with all the guns/shells/chokes/calls/decoys/blinds, but above will get you started just fine. Send me a message if you have other questions.