What is the best web-automation IDE?

I'm learning web-automation, currently just using iTerm, Watir and SublimeText, but I thought it's better to use IDE to continue my work.
What I've learned already:
– basics of Ruby
– basics of Watir and Mechanize
Now I need one good IDE to check my scripts for possible errors.
I've tried RubyMine but I'm also looking for other options(with tutorials online if possible).
