In general, you should keep to plants that come from the area where the animal evolved. A very helpful resource for checking out plants you find at your local greenhouses/whatever stores:
Edible and Harmful Plants
That website provides scientific names and some common names, but if possible, don't rely on the common names, as different plants may be called by the same common name, and a single plant may be called by several different common names!
Keep in mind that about 10 gallons is the minimum size for these guys--from what I've seen, you should estimate about 4 gallons per toad of horizontal space. There's a lot of info on this website about viv construction and some very helpful people, so have fun reading--and have fun building!