The more space you can give them the better. Wet poop will stink so keep them as dry as you can and up off the ground. They actually prefer to be up off the ground and are a lot happier and friendlier so make your cage whatever height is comfortable for you to stand at and clean out. Just be prepared to have to gently push them out of the way as they will stand in the way as you try to change their bedding especially if you've hatched them yourself and spent a lot of time with them as they've grown up. Most of ours are friendlier than our chickens.
Only use wire bottomed cages if you are prepared to keep them scrupulously clean as otherwise dried poop can cut their feet and cause bumble foot. Deep litter is a good idea and turning if over once a day will help to keep odour causing things well absorbed. Also I found feeding them fermented feed cuts down immensely on the smell but it is a lot more work (straining the food, cleaning feeding bowls etc) especially if you have them split into a number of cages, and now that my quail are outdoors I no longer ferment their food. I had a trio indoors for ages in a cage that was about 5 square feet and I only cleaned them out once a week if that. The dust was worse than the smell.
We've only kept a few - at present we have 14 adults split into four cages, and 11 three week olds. But I can't see 50 being a problem if they are dry, on absorbant litter and aren't crammed in like sardines.