What evidence and quotes support the theme of greed or ambition in Macbeth? How can I connect this to global society?

Macbeth can easily be linked to the themes of greed and ambition since ambition is one of the main themes within the play. Macbeth has many lines relating to ambition, such as:

MACBETH 

                              I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself 
And falls on the other— (1.7.25-28)

Macbeth's "vaulting ambition" is inherently connected to his greed. As he describes, he has "no spur / to prick the sides of [his] intent," but instead he has ambition which "o'erleaps itself" due to Macbeth's lust for power. 

There are many "Macbeths" in the global society. You could look at contemporary events, such as the political meltdown in Brazil, and connect Macbeth's green and ambition with many global leaders. (Dilma Rousseff is a good contemporary comparison.) Or, you could also look at past leaders who translated their ambition and greed into violence, much like Macbeth. Examples of these leaders could be Hitler, Pol Pot or Mussolini.