The values issue probably is not the most challenging part of the question. I would say that the idea of "tabbing" the values would definitely be, to me, the more confusing issue present. In terms of what might be meant by it, I would say that if you could ask the instructor, this would help out a great deal. It probably fixes everything if you could get clarification here. In my mind, I see "tabbing two values and beliefs" as being able to identify the two items and being able to know where you can find textual evidence in the book of these values. Certainly, the belief that wealthy people are "better" than others is one value that is presented through many of the characters in the book. I think you can find evidence of this in much of what Tom says and believes as well as how Jordan Baker behaves. Specific instances could be mere conversations they have regarding elitism and the sense of superiority that accompanies them simply from having wealth. I would also say that another value emphasized in the book is the futility of human action. It contradicts the first value stated, but I think it's supposed to do so. Gatsby realizes that his attempts to woo Daisy on the basis of wealth are not going to work, as well as the idea that he can seamlessly fit into the world of wealth and privilege is another instance where he recognizes that his own actions are fruitless and without much in way of endeavor. I think that being able to peer into the character of Gatsby in this capacity with specific references from the text, moments where we as the reader see this experience in its most naked and pure form would be a starting point in terms of discussion of this idea.
Numerous examples of values, or lack of values (which amounts to values) abound in The Great Gatsby that you can tab (try sticky notes or even a small piece of paper to mark each page; use the sticky note upside down with the top half extended out of the top of the book--this creates a tab).
In chapter one when Nick the narrator introduces the character, Tom, the description reveals that Tom values physical power and inherited money--lots of it. His idea of glory is found in athletic feats and pompous displays of wealth.
When Jordan tells Nick about her driving, she says that she is a careless driver who depends on other drivers to watch out for her. Jordan is careless, self-centered, and extremely egocentric. She values herself.
Gatsby values the recapturing of his relationship with Daisy above all else. He has a dream of the brief relationship he had with Daisy, and the value in anything or anyone else is only relevant to him as it contributes to his quest to recapture Daisy. At the same time, he is basically a giver, not a taker. He is extremely polite and considerate, and is uncomfortable receiving anything from others--notice how he offers Nick work when Nick is going to help him meet Daisy. Gatsby is uncomfortable with others doing things for him. He also replaces a dress for a party guest, even though doing so has nothing to do with his quest to recapture Daisy.
Those are some examples of passages you could tab in preparation for your next class. Your teacher, I think, wants you to be able to point to passages that reveal values, probably for a class discussion.