When fish are bought, usually its best not to feed for 24 hours because they're stressed and come become constipated, or they won't eat at all it can cause ammonia to be released, or worse, an algae bloom.
The only thing I use in my betta's tank is a sponge filter. They create basically no suction, and no surface agitation if you're using a valve to control air flow. They are pretty efficient, small, and simple. Also, they're super cheap.. I get mine for just about six bucks, shipping included.
Sponge filter: http://www.amazon.com/Aquarium-Bioch...7984188&sr=1-4