can you tell me whats best way to earn with my multi site

Hello can you tell me whats best way to earn with my multi site network. i use adsharing and simple ads widgets, i dont want to charge for site (pro sites). now i am available to put ads before and after post content. are there any way to put some same clickable background for all sites or banner in header or ad i siderbare? i also use popup and it works great