Endlers livebearers are easy to care for and reproduce rapidly. The best strain for real endlers is one that you like because you will soon have lots of them. I would start with only a pair or maybe a trio since they will quickly fill any tank you have.
I find that about 30 will grow nicely in a 15 gallon or slightly smaller space. I just add water, add a bit of food and wait. In 3 or 4 weeks the tank is filled with growing fry that will quickly fill your tank. I find that my wild type endlers, the real thing, will not sell well at any price that compensates me for the food and tank space. If you do not want endlers as fish to keep for yourself, breed something else.