I am not making a decent amount of money, how can I make more?

In order to make money you need both INSTALLS and ENGAGEMENT.

High INSTALLS means more potential users to get ad impressions. The longer users use your app, ENGAGEMENT, the more ad impressions and the more money you make. It's important to get high installs, but, your content needs to be engaging so users will continue to play and you'll continue to earn through ad impressions.

Here are some steps to increase the success of games you have already released to the market:

• Look at App Store Optimisation - (Description, title, screenshots) a quick google will find information on this.
• Take a look at the free ASO services like - ASODesk.com & sensortower.com 

For new apps, the KEY TO SUCCESS is: Good Niche + Nice App Icon + Good ASO (description, title, screenshots)

A good strategy for a beginner is to make multiple clones to test what works best. You can also localise these clones to have unique levels for different markets to increase content engagement, e.g. Australian specific content for an Australian release.