Hi Annie, I recently got a betta so I'm new to this, but I can help you a little.
Only 1 male betta per tank, or have a divider, they will kill each other if put together. At least 1 gal of water. Bowls are ok but they jump so you have to be careful with those.
They like warmer temps, room temp is ok unless you are me and the rooms are all around 65 deg.
Females, are alittle different. Some of the members here have a couple females together, but I am not sure what it takes to keep them from fighting because they will hurt each other as well. So I'll leave them to help you in that area.
You can have a filter and a heater and a bubbler if you want to. Some bettas like a calm water though.
If you choose not to have a filter some members say you can change 100% of the water once or twice a week and be ok.
This has not been my experience. Unless I change the water every other day, my betta's fins look like they have been shredded.
I also asked alot of questions before I got Chicken, if you want to read the thread it was a month or so ago "Let's say somebody wanted to get a betta...." That was the title, there is alot of good info in there.
Good luck