I'm interested in starting my first media buying, ad space, but don't know where to start. there's adbrite, buysellads, buyads, direct site, but not sure since I feel overwhelmed. I already have my squeeze page set up. My budget is under 50 bucks a week, but I don't know how many unique visitors a month i should look for or amount of impressions. It's for diet/weight loss niche btw.