Bug Problem - Any tips?

I have an infestation of gnats in my bedroom. Needless to say, it's DISGUSTING! I do not have any food in my room, and I throw my trash out regularly. But I live in a room in my basement, so I think perhaps the gross little buggers enjoy that environment. I have a big tub of indoor use bug control poison that is used to kill and prevent insects and arachnids for 9 months. I sprayed the buggers down two days ago and most of them died, I found most of them in my closet, where I believe they "nested" or whatever (ugh!). I sprayed that place thoroughly. Now today, I started seeing a few more of them flying around. I looked in my closet and found a few more alive. Again, I sprayed the place down. I am not a rich man AT ALL. I cannot afford the overpriced pest control services out there, especially when I am working a part-time job, bringing in maybe $200 every other week. My folks are just as poor as my and can hardly afford anything as it is. What can I do to get rid of Extremely annoying and gross nuisances? Please, please, please respond with any answers or even tips! Thank you!