I was evaluating learning WebGL for a project not too long ago. And then I discovered that the Unity engine is capable of deploying projects in WebGL.
As a newbie, you might find it instructive to learn the high level concepts of 2D and 3D graphics before delving into the nuts and bolts. Unity has its own graphical IDE with a lot of tutorials. I found it much more rewarding to learn 3D graphics when I actually had something tangible to see.