a few ghost shrimp should be fine. cherry reds would likely be to small.. but ghosts would be larger enough not to get eaten, yet small enough not to pose an issue. I would not suggest any other "fish" in the size tank. what type of filtration are you using on the tank? a snail would also be fine one of the smaller varieties. but do your research as some snails enjoy eating not just algae but live plants. I would start w/ the shrimp and do some research on snails. otherwise if you're looking for an algae eating type creature the only other "fish" i would recommend would be a clown pleco, and add a small peice of driftwood for it to hide/graze on, otto cats are also commonly suggested for small tanks but ime are alot more delicate then the lil' clowns.
what your using for filtration is also a big answer to what you can keep. otherwise if your set on having some type of "tetra or guppy" type white clouds are much hardier then either, have abit of color to them, and in general are not aggressive like danios are, or guppies. the color and fins of guppies will often elict a bettas territorial response. and as pointed out.. neons can be delicate fish to settle in and imo not suited for 5 gallons. they like being in large schools.
I would also stay away from the dwarf frogs as they are very delicate ime, and hard to feed, and keep fed. and a prime target for your betta to attack and kill if he was so inclined. gouramis are also a complete no-no, highly aggressive and territorial themselves. I would bet 1 or the other wouldn't last more then a day alive in the tank, and the betta would probably be the fatality.