I like the RubyMine IDE a lot. The code intelligence is very good – it’s so good that it tends to teach you Ruby as you use it. Code intelligence as in code navigation, easy access to documentation on the fly, refactoring, code style suggestions.
The same goes for the tooling integration. It works with most of the development tools you’d use with Ruby and captures the integration pretty well in a UI and associated workflow.
I am using both Vim and RubyMine and I strongly recommend RubyMine for anyone starting with Ruby.
Having the possibility to have a Go to definition for almost any method is great and most of the gems have great code comments with a lot of nice examples.
When I teach people to learn Ruby (I do this sometimes) among the first things I do is I explain to them how to open a gem, look at the source code, read it and then try to use it.
I cannot thank enough the maintainers of the most popular gems for doing such a great job in having great ruby code and good in-file documentation.
The same goes for the tooling integration. It works with most of the development tools you’d use with Ruby and captures the integration pretty well in a UI and associated workflow.
Link for your convenience: https://www.jetbrains.com/ruby/
(No affilition except being a paying user.)