RubyMine is very nice, but I think that I would avoid it during learning stages. It adds a lot of complexity, like most IDEs do, which can cause you to spend a lot of your time at the beginning learning the IDE rather than learning the language (Ruby) or the framework (Rails.)
If you know Java already and know no other language, I could see Java being a semi-acceptable choice. But Java truly is not a client side programming language. It's so bad for making things that don't run on a server. It requires so much maintenance and management.