In addition to all the great tips here, you can also buy Android Keyword install and reviews install, i personally use this service KeyApp.top - Android keywords promotion
Register by using this link KeyApp.top - Android keywords promotion and you will have a Free bonus installs to promote your Apps/games, up to 500 installs for free ! 
SKWAR represent super affordable app promotion packages of wide range of service: installs, reviews and ASO!!!
SKWAR is self-served platform that provides incent installs for android apps helping them to boost rankings at the Google Market and get new loyal clients. Our real users and devices in a day allow you to get thousands of installs.This leads into acquiring tons of new users and the massive growth of your business.
we provide Android & iOS keyword search installs, High retention installs, Geo Target installs. we can guarantee that all the installs are from real users, and we support multiple countries and install type for you to choose from ,get your app targeted precisely. Your app ranking will be improved in 8~10 hours once a campaign is activated.
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Hello! 
If you are looking for keyword installs, the best choice is Keyapp. We provide keyword installs both for Google Play (37 available regions) and AppStore (115 available regions). Keyword installs will help you to get an increase in app positions for search requests, so in such a way the application will get more noticeable and visible for organic users.
Besides, we provide app reviews with 30-day guarantee to help your app to get more positive feedback