I actually nursed it before in a small container. It's better to keep them in the dark so they have a good color. Dont grow a lot together as they will fight each other. The one losing will have its color fading away

Try as much as possible to get a bigger fish tank, from my experience with breeding fishes, they love having lots of space and freedom to swim about in the fish tank,

I was a beginner and I bought 5 betta fish in a small aquarium, in the morning only two were alive, I didn't know they will fight until killing one each other.

There is sometimes a bit of an "attitude" about betta fish, but I think they have some of the most interesting behavior and personalities of freshwater fish. Given enough room they are very inquisitive and active. And they do have a lot of interesting colors and forms--but I agree with OP that those with excessively long fins are effectively prevented from moving around normally and I don't like that.

I raised betta fish in the past as a hobby. They're easy to breed and crossing between types was a lot of fun.

Sadly, things came up and I couldn't find time to care for them anymore. I let the fishes go in a pond near my house. Maybe some of them are still thriving in there.

Bettas can be quite territorial, and may end up attacking each other if they're stressed or in too small of a tank, so I like to keep mine in bigger set-ups. I'm not sure if it works, but I stuck the picture of a really big fish against my aquarium overnight when my fish were getting used to the tank. Haven't had a fight happen between any of them since.