Setting up an appropriate Betta fish aquarium is critical because your Betta is confined to the world and the conditions you provide for it. Technically, there are no natural laws regarding minimum tank size or conditions since aquariums are artificial environments, and this is why care information for Bettas can be so varied. If your most basic aim is to provide your Betta with a comfortable, quality life, then there are several tank elements required to meet this standard.
An ideal aquarium setup is similar to a Betta's natural environment and should provide the conditions for your Betta to behave as it would in the wild. This means that your Betta needs space to patrol its environment, explore, and retreat into hiding spaces. Tiny tanks do not allow Bettas to be their true Betta selves! A widely agreed upon minimum tank size is five gallons, but even larger is wonderful!
It is also important to provide a filter as well as a heater that will keep the tank at a stable temperature (optimally fixed between 78 - 80°) to keep your tropical fish comfortable.
Here is a simple list of Betta fish tank essentials:
Aquarium (5 + gallons)
Lid (Bettas can jump!)
Regular lighting schedule
Heater and thermostat (optimal 78 - 80°)