Betta is not a shoaling species. The only time a betta is interested in another betta is when it wants to mate. Despite what you may get told in the shop and read online these are tropical fish that need a filter and a heater. So, yes, please do cycle and please do get a heater if you don't own one yet (50 watts is more than enough)

If you think the tank looks bare you can always try a few shrimp (red cherrie for example) or some ornamental snails like nerite.

Oh, and well done on this decision!