Hello Tyrell and welcome!
I'd like to mention that this forum has a plethora of great information at your fingertips, and is a great place to research the proper dart frog husbandry. First of all, there may be some direct and very stern opinions you receive across this forum regarding the mixing of species. So I will attack this as respectfully as possible. This is highly frowned upon in this community due to the health issues that arise from pathogens, the territorial nature of some species compared to others, the relative size difference and competition of resources, and the destruction of bloodlines. You can use the search feature to find an ever increasing and endless amount of evidence and research showing the detrimental effects of specie mixing. For the safety of the frogs, and for your enjoyment in having a long-term pet, please do not mix.
All dart frogs are beautiful and exotic in their own right, but as they say beauty is in the eye of the beholder. While typical husbandry can be quite similar across dart frog species, their vivarium sizes, and layout (horizontal footprint or vertical footprint) vary greatly. The best outlook for vivarium sizes, is that bigger is always better. Spend the most you can, and you will get more bold behaviours, provide great enrichment for your frogs, and create something aesthetically pleasing for you.
For a semi-arboreal frog, I'd recommend a 45 x 45 x 45 cm as the minimum
For a mostly ground dwelling specie, I'd recommend a 90 x 45 x 45 cm vivarium as the minimum
Of course how many frogs you can house is best determined by their size, footprint requirements, and social aggressiveness. All of which can be found in the below link.
This link is very useful in finding plenty of in-depth information regarding the husbandry/care of dart frogs.
Popular and Helpful 'Beginner Discussion' Threads
Best Regards,
Nate