My app got rejected by the iTunes AppStore for lacking functionality. What measures should I take to get my app approved?

This usually happens when Apple feels that the app is not worth downloading. And since Apple only wants to offer good apps to its users, it is important that the app is based on native functionality. 

Reducing the use of web-view can help. Secondly, offering more to your users by adding meaningful blogs, additional services and pages can also help. The idea is to make the app more meaningful and more app-like, rather than a mobile site.