RGSS
Resources on the Ruby Game Scripting System

Helpful links
RGSS 
 Reference Manual 
 Ruby 
 Recommended Reading 
 https://forums.rpgmakerweb.com/index.php?threads/slip-into-ruby-an-introductory-guide-to-rgss-for-beginners.38900/ 
 https://rpgmaker.net/articles/694/ 
 Tutorials: 
 https://learnxinyminutes.com/docs/ruby/ 
 Reference documentation: 
 RMXP: https://ruby-doc.org/core-1.8.6/ 
RMVXA: https://ruby-doc.org/stdlib-1.9.3/ 
Newest (mkxp-z): https://ruby-doc.org/core-3.0.0/