This may not apply to you but I find it so weird how many programmers won't invest even a modest amount into software they'll use 8 hours a day every day. Particularly when we'll so easily spend money to upgrade RAM or buy a new PC.
RubyMine on a cancel anytime personal license is $22.90/month (or $229 for a year). That's nothing. I'd say just try it. If you don't like it, you might only be out $23.
I'm not a Ruby person so can't comment on that really. For Java (and C++) it's a lifesaver. Things like moving a file to a different directory and it'll update all your packages and imports. Same with just renaming a class or even a method.
The deep syntactic understanding Jetbrains IDE have of the code base is one of the big reasons I use them.