From what I hear, Python is a great language, though I don't have much experience in it. Java is simple to learn, powerful, and will expose you to most of the ideas you need to be exposed to (variables with types, loops, if/else statements, functions (methods in Java terminology), along with many object-oriented concepts. But unless you're learning something very esoteric, just pick a language you like and run with it. You'll find you already know any of the concepts you need to know for whatever second language you choose.

I learned how to code mostly solving contest problems. Once you've got the basics down, I would look some of those up and see if you can solve them.