Keep the UI simple. Find a free/cheap template, throw it up, and add your code. But then... use the app. Be aware of when you are clicking multiple times to finish a task, when you have a small hesitation to parse your own icons and menus, when you jump all over the app to get something done, etc. Those are small inefficiencies to you, but broken UX to someone else. Over time, you'll have your own annoyances with the app. Fix those. And when you get real users giving you nitpicky complaints about the UX, treat them as serious breakages of your app.

Over time, you'll have a simple, usable app. And that is far preferable than a beautiful, shiny, but unusable app.