There is no wrong amount. The more bones the more water. You can't go wrong here. If you just need a little, you can divide the bones up, freeze and make broth whenever you need it. The bones in this picture were previously frozen (and still are).
Pot & Water
The more bones, the bigger the pot.
The stuff that makes broth taste good. You'll want onion, celery (I use the leaves I saved from when I cut up my veggie tray), cloves of garlic, salt & pepper. Just need to be in chuncks, you'll strain them out later.
Simmer for a bit. Needs to cook to get that great flavor. If you're in a hurry you can keep it down to an hour. If not, keep it lower and give it a couple of hours.
You'll want to pour it through a strainer. If you have meat left on your bones, let the bones cool and then pick off all the meat. You can use that for casserole or soup, Yum!
You can use it now. Or you can divide it up and freeze it. I usually don't need to divide it up (benefit of a huge family). I save leftover ice cream containers and freeze it by the gallon.