There is a version of Ruby already installed on your Mac. Do you need something special in a HomeBrew install?
And generally speaking HomeBrew installs are not a problem.
About the most common issue is where the shell initialization script gets messed up, which often turns out to be a broken PATH environment variable. A broken PATH environment variable generally results in the Terminal session not being able to find common commands.
While annoying, fixing a broken shell initialization script is not the end of the world. It just requires asking for help and then issuing some Unix commands that appear to be Gobble-dy Goop to the untrained eye (where a trained eye has spent years thinking a command line interface is a Huge step up from 80 column punched cards 🙂 )