My first game, need suggestions for updates - Bombing Run

I’m only 16 (pretty shit excuse) and made my first app. It is really simple and I am looking to add to it but I am not sure what would be best without making it too complicated. Obviously it needs more unlockable planes, my friend who does the art is working on it. I have had a few suggestions but would like to know any ideas people have. If you find an issue with the game I would prefer if you let me know here rather than give it a negative review. Link is here:
Many thanks

1,Social Networks:This is one of the best and free ways to promote your app by posting about your new app to your friends and family on social networking websites like Facebook, Twitter, Instagram, Google Plus, LinkedIn etc. On this, social website there is a lot of groups, app installs and promotion groups which you can join and share your apps or games there for free. Using forums like Quora and Reddit is very important. This requires a ton of creativity, as you can’t just go around promoting your app.

  1. Create demo video on Social Media: With the help of this method, you can upload a video demo (demonstration) to YouTube with all the information and features related to the app.

  2. Blogs:You can promote your app through blogs or discussion forums related to mobile apps by posting all the features and details of your new app.

4, Good reviews lead to more people downloading the app. Best way is to use any review exchange community . It gives more genuine reviews than paid reviews . Now a days Google has some strict policy against paid reviews . So use any good Review Exchange sites .

5, Buy good keyword installs for your app . It will boost your app ranking to top charts . I recommend which has a large number of user, and they support multiple countries . From my experience it gives more genuine keyword installs than other sites .