I'm a self taught web developer and the way I learnt is by just start coding. Write mini applications, like login and sign up. Build it like a Lego, put small pieces together to build your structure. You will be better off keeping the UI design to the last.

One of my hard learnt lessons is that web applications has to be designed from back to front and not the other way around. Understand how CSS works, theme templates are great and are cheap to buy (themeforrest) but if you didnt know how to manipulate the CSS then you will be left with a lot of frustration.