I don' have any experiances with goslings, but I'd imagine that they are pretty much the same as ducklings.
this is what I've always done.
if you are getting day olds. as soon as they arrive they need to be hydrated, ducks are much easier than chicks to hydrate, mine always found the water themselves.
you will need to go to a feed store and get unmedicated chick starter/grower. they will eat this for the first 10 weeks, then they can go on grower/finisher. they eat that until 16 weeks, then they can go on layer.
for swimming, I've always let my ducklings swim at 2 or 3 days old, but only for 1 or 2 minutes at a time, they get cold fast, then up the time 2 minutes every other day.
for bedding I used newspaper, or hay, I wouldn't use hay until they are nearly ready to go outside. DO NOT use shavings they will eat them and can die.
all my ducks are healthy..and fat, soi I guess what i did worked xD