The stocking setups I prefer are a small group of non-neon tetras. (I personally have glowlights, see sig) and a pair of ottos. Figure on supplimental feeding or the ottos dependant on the amount of algae.
If your tank had been running a relatively decently sized stock load, you could put the ottos and the tetras in the tank right away, and give it a week or two to mini-cycle for the additional load before adding the betta. Either way, add the betta last to minimize his aggression.
As for wether or not it is better off alone, My bettas are much more active in their larger tanks if they have something to chase around. Ottos and tetras are plenty zippy enough to get away from a betta (who are generally slower swimmers) so the only problems people have is when the tetras decide to pick on the betta. Which is why I don't suggest neons, as neons are IME the nippiest of the tetra family.