Are you looking for estimates in the order of "30 methods" or "300 methods"?

If the latter, you should IMO implement (mostly in order)
classes/modules Fixnum, Float, String, Array, Hash, Range, Enumerable
and Comparable. (I omitted certain important bits such as the Module,
Class or Proc classes, since metaprogramming is sort of an advanced
feature; however, they should somehow exist, obviously, maybe lacking
most methods).

-- Matma Rex