You are right, installation is not super easy right now, due to Ruby dependencies, which also depend on Nokogiri and phantomjs.
Have you seen the guide, that helps you with getting and up and running quite quickly? https://github.com/KrauseFx/fastlane/blob/master/GUIDE.md
I tried this on a fresh Yosemite installation, and it went quite fluent.
Let me know if that helps you and how I can link the guide better to make it better visible.