In addition, some species of frogs release chemicals from their bodies that can be toxic to other species of frogs. So it's rarely a good idea to mix breeds in the same tank. Frogs found in nature have a very wide variety in their diet. For example, poison frogs lose their toxicity when they are bred in captivity because their diet is no longer as diverse as it would naturally be. Realistically, we can't provide the complete variety that would be best, but keeping this in mind is a good idea.
Crickets tend to be the most available food, and generally make the basic staple for frogs.
For that type of info you're best bet is to look it up yourself, since I am considerably too squeemish to deal with that sort of subject. These can be found in most pet stores. The best way to do this is to drop some of these pellets in with the crickets several hours before they get fed to the frogs. There are also different types of powders that can be sprinkled on the bugs before you feed them to your frogs. Some specimens are extraordinarily fragile and a lot of the most common problems stem from rough handling or frogs that spaz when you try to handle them, then jump out and smash themselves on something and hurt themselves.