Racket can be a good first choice. I would nudge you, if I may, and if the lisp glove fits, into taking the deep dive into emacs + evil (optional) + paredit

Racket can be a good first choice. I would nudge you, if I may, and if the lisp glove fits, into taking the deep dive into emacs + evil (optional) + paredit + SLIME/SLY + SBCL + Quicklisp There are fully configured starting setups out there for a quick start. That's basically the closest thing nowadays you'll get to experience the interactive power of the ol' Lisp Machines. That said, you might not always need such large runtimes and other lisps can fit the bill. For example, I usually program in CL (with C FFI) for most projects, but for embedding lisps into existing C programs, Guile can be a joy. Once I was programming servo motor controllers that offered C as one of the programming languages, and I embedded a single C file that gave me a tiny little scheme interpreter and I was then able to prototype motor control algorithms and setting in way less time than before. It's just a game changer for learning about a system when you can get a REPL on it and start rapidly digging and experimenting.