Promotion for your android app is not a single action, but a whole process. It consists of several basic actions that are important for the Android platform.
You should start by creating keywords. The keyword is a word or phrase something is related to in search. To determine the correct keywords, you can ask some questions: what are the main functions of my application, what problems it solves, and so on. After that, you will get the essence, which is the basis of keywords. If your ideas are run out, you can analyze the applications of your competitors. Find the apps that are on the Top in your niche and read their descriptions and reviews. Choose phrases that may be relevant to you and add them to the keyword cloud.
For promotion for your android app, you should run the optimization. If you want to index your rating or increase its rating, you need to ASO it before promotion. It significantly improves efficiency. You can optimize the main parts of your application: keywords, screenshots, title, icon, descriptions.
Then you can start the main campaign or buying installs for promotion for your android app. Do not rush to buy numerous installs at once because such behavior is considered suspicious. You may lose your existing rank or even leave the index. To determine the optimal number of installs for each word, run a test campaign. You should make an order with 4-5 keywords and about 10-15 installs for each. Follow the dynamics of your rating, and only then go to the main ad. You may buy up to 20 installs a day until you reach the top 20. Once you reach the top 20 for a particular keyword, you should start a separate campaign to do so. The strategy for promotion for your android app is a purely individual matter. You need to follow the changes in mobile marketing and adapt to them.