How do I create UI that is quick and easy to use?

In a marketplace app, you have to focus on three key things:

Make the workflow as trimmed down as possible. Be inspired by e-commerce’s focus on conversion.
Make the app as easy to get started using as possible. Don’t think about it as an app, think about it as solving a problem and making your solution as broadly available as possible.
Understand impact points, and conversion points.