You might take a look at Julia Evans' writing as an example of this, learn, write, learn some more. Your blog doesn't have to be a reference textbook on a topic, but a log of your explorations on whatever topics you find interesting. If you have something incorrect, the worst case is nobody reads it. Best case is you start a discussion with a reader and learn something.

https://mobile.twitter.com/b0rk

http://jvns.ca/