I just know basic Win32 Console Application programming. Is it the time to learn some UI design? If so, is Qt a good choice for me? Or any other good choice to recommend? Thanks : )
Well you can pick up whatever you want in any order you want. If you are doing it before you are ready it just means you should be prepared for hardships while learning as it will become obvious what you don't understand and will have to go back and make sure you understand it before moving forward.
In fact, I sometimes recommend learning a UI or graphics library fairly soon after you have a basic understanding of the language. This is not only because you can get more interesting results (and find it easier to keep motivated in learning the language), but also because of the reason that @BHX Specter mentioned: It can become obvious what parts of the language you have neglected to learn properly or don't fully understand, and show you what you need to look up and refresh your mind on.