If you were talking about wild bettas, you would be better with subdued lighting however, if you are talking about a manufactured betta, lighting shouldn't be an issue. Bright lights however, are not necessary and if your fish is hiding more under bright lights, reduce the light amount and time.
As previously stated, you should have a day and night cycle so that the fish can sleep. That said, you can use your light as a trigger to let the fish know that food is coming soon. So, if you use a timer, you can leave the light off while you are not there and have it turn on shortly before you are there to get the fish primed to feed and swim about ( or be in "day action mode" ). If you have ambient light where the fish is, you won't need to have your lighting on for more hours than when you are watching the fish. It will sleep when that light goes dark.