What sort of app?
How you build an app depends a lot on what you want it to do.
If it’s something like expedia, amazon or whatever, something that basically just links to a web server, or is very very simple and doesn’t need to be fast and responsive then web content in a shell is doable. Otherwise I’d avoid it, it is a right pain once you start doing things that are more complex, different OS versions and things work slightly differently. They are also often slow, and often hang up a bit at times. That’s why Facebook have moved to an approach that uses mostly native code now.
If it is an action game or similar that needs quick updates, or anything to do with image processing, then web content in a shell is a real no-no.
Oh, and you kind of need a Mac ($$$) and a developer account ($99 I think) to do iOS development. There might be hacky ways to do it, but it’ll never get on the app store and onto people’s devices without a dev account.