If you plan on doing any sort of Ruby development, RVM is a must. Even though Debian does have its own Ruby packages, they're bound to Debian's release schedules, making them an inflexible option for your projects. RVM is simple to get set up, and it allows a much greater decree of flexibility, no matter what sort of projects you're working on.
This is a companion discussion topic for the original entry at https://linuxconfig.org/how-to-set-up-rvm-on-debian-10-buster