Start with the Emacs Wiki page Learn Emacs Lisp.

Not that that page itself will teach you Emacs Lisp. It will instead point to learning resources -- exactly what you're looking for here, with your question. Many users have contributed to it and edited it over a period of years. That presents advantages as well as disadvantages wrt one user's blog. The quality of suggestions there is of course various, because of the variety of inputs.

Beyond that - everything that others here have said, especially starting with the built-in doc of Emacs:

Since you've used Common Lisp it will be super easy to pick up Emacs Lisp. Consider yourself lucky about this.

If you had used Common Lisp (or Zeta Lisp or whatever) on a Lisp machine then the experience would be quite similar. You can think of Emacs as (among other things), a great Lisp environment. You can go from zero to 60 in no time, when learning.

Have fun!

Start with the Emacs Wiki page Learn Emacs Lisp.

Not that that page itself will teach you Emacs Lisp. It will instead point to learning resources -- exactly what you're looking for here, with your question. Many users have contributed to it and edited it over a period of years. That presents advantages as well as disadvantages wrt one user's blog. The quality of suggestions there is of course various, because of the variety of inputs.

Beyond that - everything that others here have said, especially starting with the built-in doc of Emacs:

Since you've used Common Lisp it will be super easy to pick up Emacs Lisp. Consider yourself lucky about this.

If you had used Common Lisp (or Zeta Lisp or whatever) on a Lisp machine then the experience would be quite similar. You can think of Emacs as (among other things), a great Lisp environment. You can go from zero to 60 in no time, when learning.

Have fun!