Kris_Toledo~
I have bettas too. Here is some basic guidelines. Bettas should be kept in my opinion in 1/2 gallon of water or higher; if they are in a small container you may need to change the water daily. If they are in 1/2 gallon of water, clean twice a week, 1 gallon water, change 1 time a week.
Next, they are carnivorous (Meat eaters) Mine likes bloodworms alot.
The temp should be about 76 degrees* Small bowls are hard to keep heated, so mine is next to the window in my bedroom.
A healthy betta will have good color, be hungry, and make a bubblt nest at the top of the water. For oxygen reasons I wouldn't seal the top of the jar. Bettas often breathe from the surface, so keep the top clear mostly.
I'm waiting on a betta tank to come into my pet store. It is a tank with a 4 way glass split, so 4 bettas can be viewed in one place. I'll also be able to put a corner filter in so the tank can cycle. As far as light goes, I don't think it matters a great deal. They are from the rice paddies of Thailand, so .... use your own judgement. Long as it has a day and night, It'll be fine I'm sure. Bettas are great fish, very hardy. Good luck,
~Melissa~