Dear Sir,
As a android Developer myself and being worked in similar project in freelancer, I understand your request and can work with you to market your app with the use of only legal ways. I will be using PPI services, Social media marketing, Forums,mobile ad networks and SEO too.
If you have any questions we can discuss it beforehand. I will be more than happy to discuss with you about any problems you have.
Thank you!!!!!!!!!!!!!!1111