Maybe you need to be honest and answer the question by stating that the feeling the story conveys to you is confusion. In fact, that might not be a bad place to start. Most of the characters go through changes in how they feel about each other more than once during the story, so maybe they feel confused at times, too.
Tom and Daisy obviously enjoy their wealth and the material possessions that it allows. Think about how Nick reacts to observing their lifestyle. Gatsby isn't as rich as he tries to make people think he is - why is he putting on the show? How does he feel about Daisy? About himself? How does George Wilson feel about Tom Buchanan and the way Tom treats him?
Pick one character and try to understand how that one character thinks, acts, feels, sees him/herself in relationship to the others. This may give you the insights you need to be able to come up with some answers for your assignment.