Problem with installing Ruby on Rails


Hi, I’m now to TOP. When installing Ruby on Rails I ran into this:
You don’t have write permissions for the /Library/Ruby/Gems/2.3.0 directory.
I googled it and the best looking advice (on stackoverflow) is to install another version of Ruby. Since it is emphasized in the curriculum not to be too easy with Terminal commands I’d apprciate guidance whether to follow this advice.
I’m on High Sierra, my Ruby version is ruby 2.3.7p456 (2018-03-28 revision 63024) [universal.x86_64-darwin17].