These are some good questions.

Choosing a skill to focus on is a combination in what your are interested in, what you enjoy, what your current position requires, and what you feel may help your career.

Learning something new and master a skill you are proficient at can be very satisfying. A great way to learn a complex software skill is to build something or some things.

You might approach this by:

• If you don't really know the basics yet, practice them - creating a new project/application/configuration quickly and accurately will make the rest go much easier
• Pick a big project you can build in pieces and work through it
  • While this might be a step-by-step course, video series, or book, picking a project and having to work it out, even with a lot digging can stick with you longer. Learning the skills of figuring and digging can also be beneficial. In your career, you will likely have many times where the resources are thin and it is up to you to work out answers to complicated questions
• Once you have built something, you can share with others, or keep a journal - either way build on it some more or build something new