Publishers want someone to handle monetisation of their website. If they get enough traffic, they want that someone to work in-house, but if they don't, they want some one (ad network) to do it for them.
Advertisers want impressions/clicks/performance.
A (successful) ad network needs to do both, so bootstrapping invariably looks something like matchmaking in the very beginning.
If you want to find my email address and reach out, I'm happy to talk to you more about bootstrapping: I've gotten more than one ad network off the ground.
Mine are at http://elmalabarista.com
Edit: The other problem you'll run into is the tragedy issue I mentioned. Your ads will be blocked by most ad-blockers' scorched-Earth policy, which comes from your shitty, unethical competitors. Good luck to ya ;)
I have some ideas about build a server-side ad-network, but because I imagine is very hard to get customers I dismiss it, for the same reason: You need to be "famous/large" to attract customer in the ad-space.