I will give you a few and then leave you to find the rest - the best way to get a good mark is to read the play after all! These should give you a few starting points though.
Although we can identify greed in Macbeth, the word doesn't actually appear in this play. Rather, ambition (which is after all a kind of greed) is much more prevalent. We know that Macbeth has "black and deep desires" from his first soliloquy and it is clear that Lady Macbeth, his "partner in greatness" has high ambitions for her husband too.
Consider Macbeth's response to Malcolm being made Prince of Cumberland:
Another key quote has to be Lady Macbeth speaking to her husband and dangling future possibilities in front of him:
Glamis thou art, and Cawdor, and shalt be
What thou art promised.
In addition, Macbeth states: "I have no spur to prick the sides of my intent, but only vaulting ambition, which o'erleaps itself, and falls on the other." It is this greed or ambition that drives the play and results in such a high body count.
Macbeth and Lady Macbeth are both characters that definitely display greed. Both characters desire more power. That’s Macbeth’s tragic flaw. He has unrestrained ambition. Ambition, by itself, isn’t a bad thing; however, in Macbeth’s case, his ambition and greed push him to seek out and keep that power regardless of the cost. For Macbeth and Lady Macbeth, the end justifies the means.
Audiences get an early taste of Macbeth’s greedy capabilities in Act I, Scene 4. Macbeth says a very quick aside before exiting the stage.
[Aside] The Prince of Cumberland! that is a step
On which I must fall down, or else o'erleap,
For in my way it lies. Stars, hide your fires;
Let not light see my black and deep desires.
The quote shows that Macbeth realizes his greed. He knows it’s there, and it scares him a bit. Perhaps it scares him a bit because he never considered that he was capable of contemplating killing a king, or perhaps it scares him because he knows what could happen to him if somebody figured out what he was thinking. Macbeth knows that he needs to keep his greed hidden.
A couple of scenes later, audiences hear this quote.
I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on the other.
I like this quote a lot. It occurs at the end of Macbeth’s monologue. The monologue is about the pros and cons of murdering Duncan. At the end of the speech, he says the above quote. It’s showing that Macbeth knows that he deeply desires the throne. He wants it bad, and he recognizes that greed; however, Macbeth also admits that the cost is too high. He just can’t muster the courage to take that final step. He needs somebody to “spur” and “prick” him into action. Enter Lady Macbeth with just such a push. She enters the scene and berates her husband for being such a coward when the end goal is so close. Her speech is probably my favorite from the entire play. Lady Macbeth paints a vivid picture of just how greedy she is and what she is prepared to do in order for her husband to be on the throne.
I have given suck, and know
How tender 'tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out, had I so sworn as you
Have done to this.
Lady Macbeth is so greedy for the throne that she would consider smashing her baby’s brains out. That’s crazy!
One more quote. This one is spoken by Malcolm in Act 4, Scene 3. He and Macduff are discussing how evil Macbeth is and who would be a fitting replacement. Malcolm flat out states that Macbeth is a greedy (“avaricious") and horrible person.
I grant him bloody,
Luxurious, avaricious, false, deceitful,
Sudden, malicious, smacking of every sin
That has a name.