Which IDE should I use for Ruby?

Answer 1

VisualStudio.

Answer 2

I have Windows

Answer 3

Use Atom.

Answer 4

depents on wich Operating System you have and what do you expect of it ?

Answer 5

If on windows, save yourself the trouble and use a cloud base one like c9.io

Answer 6

For Rails your development environment depends on your operating system.

In linux based systems you only need text editor with syntax highlight (for instance Sublime), terminal and optionally file manager (because Rails project distributed by many folders).

For windows imo best solution VirtualBox with Ubuntu server + Vagrant + text editor inside windows (for instance Sublime).
Full institutions:
https://putshello.wordpress.com/2015/03/03/easy-rails-with-vagrant-virtualbox-on-windows/

Never worked with Rails on MacOS, so I couldn't suggest you anything.