Undoubtedly, you will need to make changes and amends to your app. Each new version that you release will be another chance for you to make an impression on the staff at Apple or Google and have the potential to be promoted within the app store.
We made sure to build in a push notification function in our apps. This allowed us to send a messages to all those who have downloaded the app. This will help build engagement but can build word of mouth and downloads as a result too.