1. Would be great if you can tell us more about your audience.

2. Do you have data sets available about your users. Age, gender, income, etc because if you don't have that then don't expect to get paid top dollars.

3. I don't think you need to build anything at all. Instead of using an Ad network you can use an Ad server. You can also set floor rates at what you want to sell your traffic at. However your fill rate will be low. Best thing to do is not set any floor rate. By using ad sever I would suggest that you go hunt your own advertisers to your niche so build a sales time to get top dollars. If no direct inventory is available then sell off to exchanges. If that fails then have a backup mediation to ad networks.