I have a little 5gal with a light filter and a heater set to 78. It's normally very hot in Texas so I don't want the heater on high in case it gets boiling point in my room. I would hate to cook him.
Currently there isn't much in his tank, I am redecorating it to a theme and some of his stuff I deemed not betta safe and removed it like his rock cave. It had a rather sharp part to it. He currently has two silk plants I dug up magically from years ago when I had betta's. They were in my mouse stuff. I guess that is where all the long since passed animal trappings go. Those are not the plants that are staying in his tank though. In the end (today I'm picking some up) I want about three or four silk plants, maybe more IF there is room, two small live plants. Been looking into Java moss, moss balls, and hornwort plants a lot, two to three shrimp (help keep things clean), an Asian temple, small, driftwood or log to hide in, and some log with fake mushrooms on it. There are a few smaller detailed decor I'll be getting as well but for the most part that is my planned out set up. I brought it up in tanks that I am doing a Wonderland theme. Oh and there will be a white glass teacup for a house as well. Granted I can find one small enough to not take up too much tank.