Q:

Method cannot be called inside of a class

This program runs as intended if outside a class, how could this be run inside of one? 
class Pointester
  $points = 0

  def point_tracker()
    puts $points
  end

  point_tracker()
end

Here's the error: undefined method `point_tracker' for Pointester:Class (NoMethodError)

A:

Change it to:
class Pointester
  $points = 0

  def point_tracker
    puts $points
  end
end

Pointester.new.point_tracker

And you might want to consider using an instance instead of a global variable – depending on your use-case.