I've tried multiple forms of marketing. 1. Admob - Got users to the app, but the app did not retain those users and it was quite expensive to even get them to

I've tried multiple forms of marketing. 1. Admob - Got users to the app, but the app did not retain those users and it was quite expensive to even get them to the app. Over $1 per user for me. 2. Tried facebook ads. Just a complete failure for me. 3. I cross promote my apps within my own apps. That does ok. I'm not exactly sure the exact amount of traffic it drives, but it probably accounts for 5% of the user base on the apps i promote. 4. Facebook, Twitter Sharing. This probably accounts for 5 - 10% of new downloads within an app.