There is always varying opinions on mixing species.
Imho, I think its best to familiarize yourself with the species you are thinking of putting together. Once having been successful and actively thriving in the environment you have provided

, should they then be considered to be cohabiting with other species.
Although, I generally don't recommend the mixing of species...There are quite a few things to consider such as food consumption/waste production, habitat space (not just size of tank but also things like if they're located in the wild in the same area), aggression e.t.c. It is quite "a lot" of work in a sense. The few members or hobbyists I've read that have mixed species are very organized and keep very tight monitoring/records for everything.
So Imho, unless you are able to provide ample space and possibly suffer losses through trial and error...you may want to reconsider mixing. But as some members have said they're your animals and well your choice:?.
Here is a link to a previous thread where someone had raised a similar question
Crested geckos-dart frogs