define your target audience go talk to those people and see what they think of the app idea. visit forums, facebook groups, email people with a "personal" message ideally previous contacts, reach out to bloggers that might blog about your app see what they think of it etc. but if your having issues reaching your target market you may want to think about your app. put it out on the app store sounds like you might get lost in the app store. On the other hand, if it's skills you want to learn and it's not years worth of work why not just build it to develop the skills.