Please do not try Gouramis either. They are members of the same family as the Betta and one or the other would be brutalized or slaughtered. Probably the Betta, as wicked as the GouramI has been known to be.
Yes...the odd thing is that gouramis can be timid with other species but with both bettas and gouramis they tend to get very aggressive with anything that resembles themselves even vaguely. Try livebearers, otos or corys.
Paradise fish in a tank to themselves can be beautiful. Had a pair spawn for me years ago and it was awesome. The babies are tiny little specks when they hatch. But the male was brutal to the female until we removed her. Since the male takes care of the eggs after spawn and the fry for three days I guess he was just protecting his babies .
Voice of experience, here........ Gouramis (paradise fish) and Bettas do not mix (no matter what your LFS may tell you). Each fish by itself is a beautiful, lovely fish. But PLEASE do not make the mistake I did. If you must have both, put them in separate tanks.
And, no.... a ten gallon tank would not be big enough for two paradise fish. They need a minimum of 30 gallons. Dwarf Gouramis can live in a ten gallon, though.