It really depends on the betta though some will say you don't need the filter or need to baffle.
If the current pushes him about and it stresses him, baffle. If not and it isn't injuring his fins, it's fine.
Our Hannibal loves the filter that came with his 3.5 gallon. He plays in the current. Other betts get stressed and buffeted by filters. You'll have to observe him to see what is best for your fish.
Also, fish need a night/day cycle just like we do. You should turn the light off at night. The tank should have a thermometer and heater to maintain the temperature properly.