a few things you could do...
1. check out getting one of
these.
i know cash is usually tight in college, but it's only ten bucks, for the luxury of getting to turn your light off every once in a while
2. get a piece of sun-proof fabric to veil the tank from the sunlight.
3. plants are a great idea. java moss, cryptocorynes, and java fern are pretty low maintenance, low light plants to start off with. plus it's cute to watch your fishie take little betta naps on them. they will absorb the nutrients in your water, which should "starve" the algae. it's better to get all of your plants at once instead of little by little, because if you put one plant in at a time, that just gives the algae a chance to start growing all over it.
4. is your light incandescent or cf? if you have incandescent, i would suggest switching bulbs ASAP. incandescent only encourages algae growth. the cf (twirly) bulbs are available in kelvin temps and phosphors much better suited to growing plants. 5000K to 6500K is a good range.
5. if you're getting a lot of algae on the sides of the tank, perhaps invest in a magnet scrubber, or one of the old fashioned "scrubby pad on a stick". if you go this route, look for ones specifically made for acrylic tanks (i assume that's what you have).
6. take extra care to make sure you're not overfeeding (i doubt this is the case, as most bettas are little piggies who will chase sinking food right to the bottom, but you never know.)
7. an oto or a couple caridina japonica shrimp. while you shouldn't depend on your creatures to keep your algae at bay, it helps. and they sure are cute. this would arguably be overstocking your tank, though, so you would probably need to do more frequent water changes.
8. speaking of water changes, do you know what your water parameters are? if you wait too long between changes, or if your tap water is abnormally high in nitrates, phosphates, etc., that could be encouraging the algae.
