Plate tectonics is the closest thing the field has to a theory of everything and a relatively superficial understanding plate tectonics will give decent insights when looking at large scale structures. At more intermediate scales id recommend picking up a geology book about a region you are somewhat familiar with or have traveled through. The roadside geology books series are usually pretty good, id recommend picking up the one for northern California (https://www.amazon.com/Roadside-Geology-Northern-Central-California/dp/0878424091) and reading the section on the cascadia subduction zone (which is very simple relative to the rest of the state). I will also caution you probably won't ever get very good at identifying small features. Professionally, I am a geophysicist and while I have a lot of formal training in geology working in the field with actual geologists aways impresses on me that people really only develop good geologic intuition by doing lots of mapping in the field.