I actually only know CL and Elisp. I played a bit with Clojure, and its Emacs story looks pretty solid, but I was thinking it might be difficult to translate idiomatic clojure code to Elisp when Clojure has more emphasis on purity.

I'd guess that CL is closest to Elisp, especially when you use the popular "cl-mode", and you have the same mental model of hacking on a live lisp system. I learned CL from Paul Graham's "ANSI Common Lisp" back in the day, but I'd too be interested in what's recommended in 2021.