Hey Maggie,
I saw that there were no replies and thought I would try and help you out. I have been breeding RETF for 4 years now and love them more every year. Here we go:
1. RETF do well in larger groups. I keep more males then females, one group is 4 males and 3 females, because I have had times when two males were going for the same lady and would totally ignore the other females. The size tank depends. For everyday keeping I use 20 gallons for the first pair and 5 extra gallons for each additional frog. 2 frogs 20 gal., 4 frogs 30 gal., ect. This is more then some will tell you, but I would rather give more space then to little. For breeding I have a 90 gallon acrylic rain chamber, a smaller 70 gal., and a converted shower stall. I don't have a set formula for how big you need per # of frogs but again better to be a little roomy then too small.
2. I am not sure I know which species you mean. I have heard the Australian red-eyed frog (Litoria chloris) called a Ruby Eye before. I have never kept these, but they are in a book I have by Philippe de Vosjoli called "Care and Breeding of Popular Tree Frogs". I would get this book anyway as it is excellent for RETF regardless of what species you are talking about.
3. Ok if by Tiger Leg you mean (Phyllomedusa hypocondrialis), as there is some confusion between some species, they will be very similar to RETFs in their care but just a little drier. As for the South American Clown Frogs, they are rainforest dwellers from the Amazon Valley. So I keep mine warm and wet. I have never found a goup care sheet on these so if you find one let me know. I keep mine similar to RETF in temp/humidity but give them a little more of a gradient to chose from. One side is warm and humid with an undertank heater under a water section and the other side is cooler and a little drier.
I am in no way an expert on these frogs, but only mean to be helpful. I suggest you get as much info on them as possible. And as funny as this will sound, beware the internet it is full of bad info. I would try breeders in your area or even local zoo/aquariums for more info or even a tour of their frog room.
Thanks,
Rob