Speaking as an advertiser, I only work with networks that are recommended by friends in the business. If they've already worked with a network and know the traffic is solid, I'll give the network a shot. Otherwise, some no-name network cold-emailing will just get ignored - it could be a great network for all I know, but there's no reason to open up risk like that when I can easily work with guys who have already established their credibility. So I would say just work on networking and meeting guys in the industry, improving your contacts, etc
Also if the network is too slow with getting the offer up and running (ie. they take multiple days to set up the pixels, constantly request more and more changes to the point where it's taking 2+ months just to get 1 lead) then they usually end up on a little shared blacklist. Likewise if they're too eager and they just plop it up and want to immediately run it 1 day after first contact, it makes it seem a little sketchy. So make sure your shit is nice and professional and you know what you're doing so there's no awkwardness making you look like an ass and giving you a bad rep.
Also, when a network asks for ridiculous terms, the first thing advertisers do is drop their name in a group chat so everyone can laugh about it, and that's a good way to significantly put a damper on your potential business.