mkcookin's right, I have been advertising with Facebook too and the wide array of filters can get you the targeted visitors you want. From location, to specific interest, age, likes and so on. I just dont buy CPM as I pay much more with it for my niche so I use CPC, but it still depends upon you. Trial and error is still the best option.
What kind of site do you have? It might change some of our recommendations.
In addition to Facebook ads, don't forget about advertising on Google/Bing/Yahoo. You can greatly customize your target demographic to pinpoint your exact audience. You could also target specific sites and offer to pay them to do a post, article, etc, about you.