Not having mentor-ship or responsive management is difficult. Not knowing what to learn or where to focus is definitely frustrating, and having to do it all yourself is probably the hardest way to go. Having said that, learning another programming language is almost always useful, but don’t get bogged down in the minutiae of individual code segments.
If you know where you want to be/what you want to be doing, check out what sort of things companies that have that sort of job are also asking for. It might be a particular set of languages, but usually there will be soft skills or other experience they want. That might help you narrow down which language or languages to focus on.
And if it doesn’t, noodle around a little in each and see which you like. Doing things you enjoy is much easier and generally more amusing than doing things you merely tolerate.