[malandrew]

Javascript. You have to know it for a web app, so start there. Build the front-end in it. Once you get decent at the front end, you'll know a lot more about programming so you then make a much more informed decision regarding a backend language and framework that works for you. Could be ruby, python, php, clojure, scala, etc. or even more javascript. Delay the decision of which back end to learn to the last responsible moment.

[askar]

That's a great advice. I would say, in this day and age, if you are starting to learn then learn it correct. Learn a JS framework like Angular and build your client as purely browser based and learn another framework such Ruby-on-Rails or Laravel or CodeIgniter to just serve JSON data for your JS client. I think that's the route to go as your data feeds can be leveraged on many different mobile clients as well.