I have a very strange opinion about this. First off i dont believe any language per say is really better than another simply more efficient at a function , so based on what you wat to do , you CAN choose a language to specialise in. BUT and here what ive learnt from many developers i consider legends , markup languages funny enough can be found in any book , a develops real asset is his ability to logically solve a problem. Once they have a logical solution using a code is easy , and they can pick up any book and apply it.
I would say start by knowing sort of which direction you want to head into , this will probably change, learn by doing , analysing code and why its the best solution , another solution inst as good. If you get the logic behind a language you have most of it down.