I see a great future for this - hopefully will get more users hacking on embedded devices with Ruby codes (ruby + Arduinio or even Routers - e.g. OpenWRT).
Quick glance in the Make file, sees runtime libraries for Win/gcc/iOS - should be able to build an arm exe easily.
There is no shortcut to knowledge - do, fail, rinse and repeat, until you understand. Until you have installed, understood and successfully ran a rails app, tutorials are just next to useless. Apply apply and apply some more.
Follow this guide and http://guides.rubyonrails.org/getting_started.html, and don't slack.. Understand every line before you move on..
Excellent introduction.