What you really need.
1. a 2.5 Galon Aquarium and up, yes. you can cycle a 2.5 galon tiny aquarium. a Betta Fish, live plants and with the good ol' friendly bacteria!
2. Filter, you need a filter to keep the water clean, yes. they can survive with no filter, but will get weaker and weaker due to dirty water, get a filter, makes maintenance easy. I got a 3-watt mini submersible power head/filter, added some diy top filter made from HDPE plastic bottle. also added 4 holes to even out the flow of the water, Betta's likes calm water.
3. Add a heater if you live in cold places, I live in a tropical place so no heater for my Betta.
4. Ligthing, to cycle day and night.
5. Some live plants, unpainted resin cave/barrel and silica sand/gravel to house friendly bacteria. I got the Pothos Plant for my Betta.
That's all. the end. life is easy, enjoy your aquarium.