Oh boy, you are in for a treat. What kinda goats you got there?
Goats will eat anything they can get their mouths on. They will generally not eat grass; they are browsers. They will eat things that don't even seem like they'd taste good. They will eat things deer won't eat. I have recently tried to plant some baby conifers in my goat yard...They were demolished. Goat-proof their enclosure before you get them...You don't want them eating plants that are toxic to them (and they will, they really do not know any better).
The good news about this is if you need an area cleared, goats will all but clear it for you. They pretty much fixed my privet problem in their area.
Alfalfa should be provided if you don't have quality browse. You can find it at feed stores, like Atwoods,
Tractor Supply, etc. Make sure they're eating it. This roughage should be most of their diet. You'll want to get grain pellets (I use Ranch Pro) for them, but make sure it's for goats...And don't feed them grain exclusively. It's bad for them.
They need salt too (with copper, unlike sheep which die easily from copper OD). Get the salt in loose form. Don't give them a block; it's very bad for their teeth.
Are you getting whethers? If so, they are prone to kidney stones. You'll need to make sure the salt/food they have has ammonium chloride added. This will prevent stones. Also, the "don't feed them too much grain" goes double for whethers.
Also, you need your dirt tested for selenium, if there's no information available already on selenium content in your area. A lot of regions have selenium-deficient soils, which makes the browse selenium-deficient. Goats on selenium-deficient browse will need regular shots of the stuff.
Also I know this isn't food related, but a lot of people don't know you're supposed to trim these guys' hooves...
Good luck with your goats! They're an absolute joy.