I want to become comfortable with software development. Where should I focus on?
The following statements are true.
The right set of skills, combined with solid fundamentals, makes knowledge acquisition easier.
Combining strong fundamentals with a software engineering skill-set unlocks any topic that you might want to learn. Focus on these things first, and they will serve you for your entire career.
The above points are from this article.
Chris Lee writes well on this topic and executes his ideas in Launch School.