[Mugwort]

Get a copy of Racket, take notes, type in the programs for yourself, experiment. This video is the best most direct introduction I have yet found.

https://www.youtube.com/watch?v=a5p8DPbaokE

Learning Lisp, Scheme or Clojure is more about learning ideas than anything else.

Later you might want to learn Alonzo Church's Lambda calculus after learning some set theory and mathematical logic.

[dreamcompiler]

Racket is not Common Lisp. It's not a bad idea to learn it, but the questioner specifically asked about Common Lisp.