What Programming Language Should I Learn?

I'm looking to learn some programming. 25 years ago or so I learned a bit of Turbo Pascal, but I haven't used it in ages.

I'm getting back into gaming, and looking to start a server and community. I'd like to do some developing for it. A lot of it is LUA, with some C#/C++, as well as JSON.

For someone who would call themselves a beginner, what would be a good language to learn to get back into it?