Revenue share for promotion of mobile apps

I'm a sole android app developer with good quality free apps (games) but not much experience in marketing and promotion of my apps.

My biggest problem is that I have little money to promote my apps, so I'm looking for advertisers who I could share my revenue with (from ads) in exchange for promoting my apps.

The apps do make real good money, unfortunately without real promotion they won't last very long.

I have searched the web and contacted some top developers (1M+ installs) if they would promote my app, but hadn't any luck so far.
Therefore I'm asking here, in hope that someone knows where I could find such advertisers.

Thanks in advance!

A mobile ad network is the way to go. Choose one where you can be both an advertiser and a publisher, then use your publishing revenue to promote your app.

Once you've made some revenue, if you want to have a direct one-to-one partnership with a publisher to maximize ROI, there are a few networks that can facilitate that too.

If you do actually have a good install base and frequently recurring users, you could make use of a mobile ad network first, until you can build a proven record of delivering adverts to users (and getting engagement). Once you have that, you can consider approaching content relevant advertisers directly - yourself.