When examining the role of Gatsby in this chapter, you need to think about how he relates to other characters. Chapter 7 features primarily the conflict between Gatsby and Tom, and their battle over Daisy exposes problematic idiosyncracies of both characters. Note how in previous chapters there have been veiled hints about Gatsby´s criminal activity, and Tom discovers the truth of these accusations. Tom uses this knowledge to disgrace Gatsby.
We can see too that Gatsby is trying, vainly, to recapture a perfectly happy blissful past. This makes him order Daisy to tell Tom that she has never loved him. Gatsby, perhaps because of his own insecurities, has to know that Daisy has always loved him alone and that he has had her loyalty. When Tom orders Daisy away, Gatsby declares to Nick that his dream is a failure.
Of course, centrally, Gatsby´s decision to take the blame in the place of Daisy demonstrates both the depth of his love for her and his honour and code of chivalry that captures so much of his character. Although Daisy seems to treat him abominably, he still willingly sacrifices himself for her. A key image to focus on is when Gatsy watches Daisy outside her house whilst she and Tom sit together inside. This somehow captures the love Gatsby has for Daisy and also helps the reader move beyond his criminal connections and sympathise with his lot. Note too, how Nick´s departure at the end of this Chapter mirrors his first meeting with Gatsby in Chapter 1. In both of these incidents, Gatsby is solitary in the moonlight, lovesick and pining over Daisy. Pay attention too to the differences: in the first meeting he is stretching his arms out across the water towards the green light, showing optimism about the future. In this chapter, however, he is placed beyong the green light and is on teh lawn of Daisy´s abode, but his dream is now irrevocably lost. A tragic ending to his hopes.