How to increasing app downloads on Google Play (organic and incentivized install)

Dear BHW Community, I am starting this thread to share tips and find out what mobile marketers and developers do to increase download of their apps.

Organic: Standard app store optimizations and reviews work. But they wouldn't get you to the promised land.

Incentivized installs: I haven't found any inexpensive or reasonably priced way for incentivized installs. There is Google Adwords and Facebook. But its way too expensive.

Is there a more cost effective way to get incentivized installs? I am talking about >1K installs a day for a few weeks.