The prerequisites for working with ruby are you need a working OS of least 256 ram and 4 GB hard-rive.Its no matter which OS you are using,you can use windows PC or Linux or mac.Installation of ruby should done before you working with ruby.
Ruby is an fully object-oriented programming languages with sugar syntax which help developers to write program easily and fast with out doing extra works for creating new standard API's.
Working with ruby provides many options,you can work with console by executing ruby directly from the console.For example
$ruby -e 'puts "Hello World"'
or you can work with ruby files,put the program inside a ruby file and save it as ruby file by saving file.rb after that run from console.for example
the third way to work with ruby is,Work wit irb(interactive ruby),ruby provides a environment you can executive ruby programs.To go to irb,type irb