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.