I would say all of them, at least at first. Eventually you will probably develop a preference for Scheme or Common Lisp, but they both have enough differences that it's best to get a handle on everything that's out there.
Scheme has continuations for example, and it's good to learn about those in Scheme, even though they can be implemented in Common Lisp.
Learning the difference between lexical and dynamic scope is important, and if you learn both Common Lisp and elisp you'll come across the implications of both.