I just received a new Mac with Apple Silicon (M1) and decided to install everything from scratch, including Jekyll (and Ruby, Bundler, Webrick, and other dependencies).
While I designed this video for someone setting up a new Mac with Apple Silicon, it should work just fine on Intel. Please be aware I did not test these instructions on Intel, so maybe there are differences, but I do not think so.
Video: Install Jekyll on Apple Silicon
The video is about 30 minutes long. I followed the video as it went, and the total time was 40 minutes for me. Set aside an hour if this is your first time, and you should be good to go after that.
If you are familiar with using the Terminal app on your Mac and need the steps, here is a link to those instructions:
The instructions are in a readme file on GitHub, so feel free to submit a pull request if anything needs adjusting.