1) before anyone else says this, do a search. click the search button, type something, click search again. do some more search
2) you're not going to be getting anything for "a few dollars" you could buy an oil change for "a few dollars"
3) if you want REAL performance gains you could a) get a new car b) get an H22 swap or c) go forced induction which

all of the options under 3) goes for about $3000+