One thing I try to do is read everything that is considered well written or canonical in some way.

These types of resources tend to be informative, easy to grasp and often inspiring. They are things like books/textbooks, blog posts, tutorials(most tutorials suck though). They will usually reference other (even more canonical) resources so you shouldn't really have problems finding new stuff to read. You can pick and choose based on what sounds interesting and repeat.

This has been extremely efficient for me, and I have learned a lot pretty quickly.