Any easy way to make an ad deal?

I have a web game https://katan.io/ where I show ads to users using adinplay. As I've read & understood if I am able to arrange a deal with a suitable company to show their ads, I'll be earning much more than adinplay ads.

I've talked with a fellow game developer who has tried a similar path but failed & lost many months. I don't want to lose weeks and getting nothing in return.

So I am looking to see if anyone has successfully done this and what types of tips you can provide me with?

Note that I've posted on related subreddits, emailed many game sites etc. but so far nothing.