mantellas mostly are WC, they need cooler temps and it can be hard to find food small enough at times, although some of the mantellas are stunningly colorful! white's tree frogs, waxy monkey tree frogs and red eyed tree frogs are somewhat easy to care for although a ten gallon is not really the best size terrarium for them as they prefer more height.
i thought you already had snakes?
yes, my avatar is a "blue" phase white's tree frog. out of all my reptiles, frogs, and inverts the inverts are the easiest to care for, particularly the "dry" species (brachypelmas, aphonopelmas, grammostolas, etc.).
Yes, they are wild caught and some need cool temps. This does not mean they are not hardy and easy to keep. As for food items, a fruit fly culture can be easily started and small sized crickets can be ordered. Captive bred animals can be established only if wild caught animals are worked with to begin with. If you do the research and set up the right environment and temps then they are as easy to keep as Dendrobates. I even know someone who breeds Mantella laevigata. I tend not to shy away from animals that sound difficult to keep, but that's just me. I like the challenge.