What can i add to my tank?

Got a 10 gallon with a male betta and an african dwarf frog. Currently i don't have a filter but i can get one. Im not a big fan of bottom dwellers but i like shrimp. And hopefully i can put some pretty fish in there? what kind? Don't worry im a responsible fishkeeper so i wont just go out and buy anything, just looking for advice. The reason i gave my filter away was cause my betta seemed agitated by it...