My suggestions for good "starter" frog/toads would be:

A common species of Bufo toad -- sedate

African Dwarf aquatic frog -- totally a swimmer, eats granulated food, no bugs to deal with

White's tree frog -- needs the tall tank setup but mellow

Fire-belly toad -- they can be lively jumpers and I had one that could even climb a bit, so be careful when cleaning tank.

I had American bullfrogs; they were jumpy and more afraid of humans, but cool -- if you have a good net and a big tank or pond.

Northern leopard frog -- more active -- hard to catch if they escape.

My experience has been that it's best to keep one frog or toad per tank; I've had some instances where one of a pair would start to hog the feeder crickets and then the shyer one would start to starve. I even lost a few before I figured out the pattern. Often it was a male/female pair and the female would not let the male eat. This can be solved by feeding them separately, although sometimes handling them makes them nervous and then they aren't interested in the feeders.

That's one reason why I just have Bluebell now, and if I get future frogs or toads I think I'll do the one individual per tank thing.

Hope this helps!