In this question, we are not told which topic you picked. However, we can still analyze how this quotation relates to other parts of the book.
In this section, we are once more introduced to the theme of appearances vs. reality. We see that Gatsby looks fancy and put-together. However, his eyes look tired and he looks pale, which shows that he might not be as happy or calm as he appears. Moreover, it appears as if the confidence that Gatsby shows through his clothes is not translated into an inner confidence.