Keywords are your most powerful tool.
Choose niche keywords to target the long tail of searches. You can use tools like SensorTower, Mobile Action and Google Trends, to identify keywords which are trending, have a good number of searches on them, but have little competition from competing games.
It is a good idea to plan your game around these niche keywords. E.g., once you have a good keyword, try to build aspects of it into your otherwise standard platformer. This will make the keyword relevant and help with downloads in the long run.
Study your reviews. This will identify wording and phrases which your users associate with your game. Using these as keywords will increase your search results.
Optimising your keywords should be an ongoing process. Experiment, update and measure the effectiveness of your keywords as often as you can. This is the cheapest and most controllable of all your marketing efforts.