So, I am pretty new to the whole fish owning thing but I am considering buying a 10 gallon tank when i have enough funds to do so. (i'm a poor college student

) Anyway, I am considering getting a betta for the tank but am not sure what some good compatible species will be. All we have in this little Podunk college community is a Walmart so my options are pretty limited. (I actually bought my current betta fish at a Petsmart in Saint Louis where i live and drove them to my college because the betta supply is so crappy at our local Walmart. Half of them are always dead and the other half just don't give me alot of options for what i want.)
Anyway....A few questions I have concerning this:
I know the other day I saw fiddler crabs (i think that is what they were called) and I was wondering if a couple of those could do well with a betta fish. And if so, what do they eat and how do i get the food down to them?
Would a bottom dweller sucker fish work in a 10 gallon? And if so, same questions apply as with the crabs.
What other species of standard fish would work too? I'm sorry that I am not familiar with the names of my common species so I'm not positive what exactly they have at my walmart. I'm going to look as soon as i post this so i could update with species names later if anyone wants.
Any help or advice would be appreciated, thanks.