Most companies seem to prefer folks who have a broad base of general computing knowledge plus one specific area of expertise. This is sometimes called a "T-shap

Most companies seem to prefer folks who have a broad base of general computing knowledge plus one specific area of expertise. This is sometimes called a "T-shaped programmer". There are definitely exceptions, but is a good place to start. Other than that, practice, practice, practice. And get out of your comfort zone when you practice, don't just do things that are easy for you. You are only learning when it is hard and it makes you wonder if you might be stupid.