Thanks for your help, I basically need to decide between a floor-dwelling and tree-dwelling dart frog now.
I've ordered "Poison Dart Frogs" by A and S sihler to read, and I'm still finding useful bits of information on the internet.
I think as soon as I've decided which frog, I'll buy the vivarium and make sure I can keep the conditions stable, while breeding some fruit flies. Once I know I've got the basics down, I'll start looking at where to get the frogs!

Thanks again