First of all, this is a saltwater forum so you usually won't get much help here. However I do happen to know a lot about freshwater bettas. They definitely do not require a tank 50 gallons, putting a single betta in a tank that large would be, a waste and if I don't say so myself, a very boring tank. The most common species of the betta fish (much less colorful but still the same) live in shallow puddles in Vietnam. These fish do not require large tanks, anywhere from 1/2 gallon to 5 gallons, I wouldn't go any higher than that, it would just be a waste, unless you've got a real thing for this betta. All the bettas you see in those little bowls at fish stores are males and they're kept individually for a reason, they fight to the death with in the same tank. You can get more than one per tank if you get a specific bowl or tank that has a divider between them. The only females that you see are in larger tanks and can be kept together peacefully but require warmer, larger, and better water conditions than a male, they are also considerably smaller than males. Bettas do not require a heater they can survive just fine at room temperature water. For the novice aquarist I would recommend buying distilled water, I'd also recommend using a betta water conditioner. Bettas can be fed many types of foods, they're not at all picky, small floating pellet is just fine. Bettas also have a habit or making this bubbly, white, foamy stuff at the surface of the water, this is so because they are trying to make a breeding nest, however, because most bettas are not included with females, this white foam just makes the tank look gross looking and will require frequent water changes. The beginning aquarist may be able to keep there bettas for (if there lucky) 2 - 3 years, BUT with proper care, they can live for much longer than that.
I hope this was helpful because it took me a VERY LONG TIME to write lol Anyways glad to help out! :joy: