Hi, and welcome!
An important thing to realize is that a larger tank (within reason) is generally less work to maintain than a smaller one. In addition, a larger tank will hold a more steady temperature and water chemistry. So, a 2.5 gallon tank is easier than a 1.5 gallon, and a 5 gallon is easier than either. Look up the sticky with "Old Fishlady's water change recommendations" and you'll see what I mean. Another reason to go with a 5-7 gallon is that it is reasonable to establish a nitrogen cycle with a tank of that size, should you decide to go with a filter in the future. It also leaves open the possibility of dividing the tank in the futures for 2 bettas.
Light requirements partly depend on what you decide to do for plantings.
You will probably want to have some basic meds on hand for emergencies.
Wander around on the site, especially the "stickies"; there is so much information here!
An important thing to realize is that a larger tank (within reason) is generally less work to maintain than a smaller one. In addition, a larger tank will hold a more steady temperature and water chemistry. So, a 2.5 gallon tank is easier than a 1.5 gallon, and a 5 gallon is easier than either. Look up the sticky with "Old Fishlady's water change recommendations" and you'll see what I mean. Another reason to go with a 5-7 gallon is that it is reasonable to establish a nitrogen cycle with a tank of that size, should you decide to go with a filter in the future. It also leaves open the possibility of dividing the tank in the futures for 2 bettas.
Light requirements partly depend on what you decide to do for plantings.
You will probably want to have some basic meds on hand for emergencies.
Wander around on the site, especially the "stickies"; there is so much information here!
