That is not good advice. Ruby on Rails is widely used. Java would be a good option, but it would probably not be something that could be picked up as easily or

That is not good advice. Ruby on Rails is widely used. Java would be a good option, but it would probably not be something that could be picked up as easily or as quickly as something with RoR, Python, PHP or JavaScript. C# would narrow your options much more because it would lock you into the proprietary MS world. Something with iOS or Android would be preferable. Note: I'm not saying C# is bad, I have used it and will again. I'm just pointing in the direction of what could be picked up and then turned into a career move skillset in self study timeframe.