Having a clean, efficient UI is important for more than just having your game look pretty while you play. A good UI set up helps you filter out unnecessary information so you can concentrate on what you need to know in order to maximize your performance.
I’m going to explain not only how I set up my UI, but why I have it set up this way. All the screenshots in this post link to full size (2474 x 1392) versions so you can clearly see my setup.