I think you have tried both PPC and Affiliate Ads, but now give a try to CPM Ads.
What is CPM Advertising?
CPM
is an advertising term which means Cost Per Impressions it is one of
the best marketing strategies in terms of web traffic. From a Publishers
point of view how much a common blogger could earn from thousand page
views that he receives from his Blog, some CPM ad network pays $3/1000
Impressions while other pays $4/1000.
How CPM Advertising Works: