SEO suggestions

Im still pretty new to SEO but I have a few adult tube sites that are making me between 6 and 9 dollars a day. The best site gets about 7700 UV a day and seems to be slowly increasing. Google just recently ranked it as a pr 2 but someone was saying I need to monetize my site to bring in more $ but didnt really go into much detail on it. Does that just mean I need to buy hardlinks basically? I've also just started using no hands seo to build backlinks which I guess is working ok but could using these automated backlink tools cause Google to sandbox my domain and should I just be more focused on doing manual backlinking to high pr pages/domains? Also what backlink.services do you guys recommend? As I've been using backlinks genie since they have a $10/month plan. Is there anything better that costs slightly the same or even a little more?