Hi there, you mentioned that your FB has 24000 likes, I would highly recommend you take advantage of it. You can hold activities to attract users to download your app.

You can also tell your followers to complete a certain task, for example, invite friends to download your app. Rewarding the one who bring the most downloads publically each day.

Besides, you should also increase your app ranking on the app stores, because over 65% users discover new apps by browsing or searching on the app stores, and most of them just browsing the top 10 apps. You can increase your app ranking with the following methods:
· Optimize your app keywords -When you’re selecting a keyword, you need to take keyword relevance, traffic, and competition into account.
· Optimize your app title - It should include the keywords, which can increase your app ranking by 10.3%.
· Optimize your app description -Add 8~12 keywords in it（Google Play Store).
· Get app installs - which can boost app ranking in hours, highly recommend.ASOTOP1(http://www.asotop1.com/?from=cr-chris) provides this service.

Besides, you should also get positive app reviews(http://www.reviewapp4u.com/?from=cr-chris), because most people wil check the app reviews before downloading it, and iews from your former or existing users and choose your app. What’s more, data shows that 80% users have changed their minds about downloading an app based solely on the negative reviews they read.

Hope these methods are useful to u.