I would think that most medications that are used for poultry would be safe with geese as well. Some prescription drugs such as Baytril (antibiotic) and Metacam (pain killer) are safe for geese. I used Metacam for my older goose that has arthritis and I have used Baytril many times on my poultry (ducks, chickens, etc.) For dewormers and other medications that are purchased over-the-counter, just be sure they state "poultry".
As far as having things on hand, I keep povidone iodine, neosporin (without pain killer), gauze, epsom salt, polyvisol (without iron). Hope this was helpful.