Hello,
I have chosen to do this incredibly cheap as I am new to freelancer and looking for reviews.
I would combine Facebook Ads (targeted at the appropriate demographic that exhibit behaviours suitable to downloading games), Social Media, and influencers (people with large followings who will plug the app).
This will increase downloads and organic reviews, which in turn will fire you up the rankings and create even more plays and reviews.
Let me know if you have any questions, i'm happy to help!
Thanks, have a great day,
Tom