well that depends on what you mean by good advertising? do you need cpm or ppc? and is it by uniques or looking for increase in traffic or conversions?
Cheap and good...These days? Those are 2 opposing words. Just like saying Right-Side up up-side down. You get what you pay for, you buy cheaper traffic, you are going to effectively need to spend more because your returns are going to be less. Where as buying high quality traffic, you might need to buy less to get more results. Keep that in mind.