I struggled a little to get a basic NSTableView working in RubyMotion, coming from an iOS background, as I couldn't find any conclusive 'hello world'-esque examples. So, here's mine.
It's also useful to see how to create your first window, as the difference between NSViewController and NSWindowController isn't immediately obvious either. There's a helpful explanation of this on StackOverflow.
Once I'd got it working, I converted it to use AutoLayout. Note the sequence that I use to setup AutoLayout:
init_views configure_views place_views constrain_viewsa
I find this sequence helps categorise what can be a complicated setup (if it were a more complicated controller, at least).
To get started (note that RubyMotion 2 is required for OSX support):
$ cd motion-nstableview-example