well you need to find out what kinds of turtles you can actually get. If you get them through a store you're probably limited to 2...
maybe 3 species.
I'm lucky enough to have a
Reptile "show" where dozens of breeders bring their stock in to sell. They're very knowledgeable and have a huge variety of species. You'll have to see if you have something similar near you.
(They call it a "show" so they can operate like a zoo and not deal with all the licensing and taxes that pet stores endure...but they're definitely there to sell)