Boost App Purchase Conversions

My app has a steady stream of downloads, but too few users are converting into paying subscribers. The priority is not generating more installs. I need to identify what happens after installation and improve the install-to-subscription funnel... (Budget: $30 - $250 AUD, Jobs: A/B Testing, Analytics, Android, Conversion Rate Optimization, Data Analysis, Google Adwords, Google Analytics, Internet Marketing)