To be a UI tester, specifically UI automation, I would recommend, highly, that you take some basic programming courses if you don't already have them. Something in JavaScript or Python especially. While you can get away with record/playback for the short term, eventually you're going to need to be able to build logical structures and decisions that go beyond just macro recording.
This isn't a bad idea for a manual tester as well. Knowing how application code works helps you target your tests towards those "fragile" places of the application.
While you can get all sorts of technical skills, one thing I've discovered over the years doing UI Test Automation is that it takes a certain mindset to do this kind of work. You need to have a high level of creativity for example. Manual steps may say to perform a certain task. However, when it comes to the automation, you may not be able to fully implement the EXACT manual steps due to restrictions on accessibility to certain components. A creative mindset will allow you to start thinking outside of the box and look for other ways of performing the same task that still tests the same functionality.
In addition to creativity, you need persistence. You can't just give up the first time because something doesn't seem to work. Dive deep, figure things out, keep working at it. The answer is there somewhere.
And finally... communicate. You are not in a box. Too often testers are separated from the developers. Break down the silos and sit with the developers. Show them what you are trying to do and, perhaps, they might be able to help you find what you need to do the testing or even build in some sort of hook for you. Anything that will help the developers gain confidence in their code is a good thing.
