One of the aspects of contemporary society that Fitzgerald always seemed to write about, at least to some extent, is the American Dream. Here, in this story, clearly Dexter is an excellent example of somebody from more humble roots who, by hard work, manages to get ahead and become part of the "new wealth" of society. He is clearly described as being different from the "old wealth" (those who inherited their wealth rather than earned it):
All about him rich men's sons were peddling bonds precariously, or investing patrimonies precariously, or plodding through the two dozen volumes of the "George Washington Commercial Course," but Dexter borrowed a thousand dollars on his college degree and his confident mouth, and bought a partnership in a laundry.
Note how Dexter is compared to the "rich men's sons" who seem to be rather ineffectual in terms of actually going out there and earning money. Dexter, on the other hand, shows that he is "newer and stronger" by his get-up-and-go spirit.
However, apart from his ability to make financial success come true for him, what is interesting is that his "winter dreams" have focussed on attaining Judy Jones, not just becoming wealthy:
It did not take him many hours to decide that he had wanted Judy Jones ever since he was a proud, desirous little boy.
To him, Judy represents the confidence and carelessness of the wealthy. Note key descriptions of Judy that associate her with gold, such as "a slender enamelled doll in cloth of gold." Fitzgerald is keen to associate her person with the dream of wealth and success that inspires Dexter to quit his job at the beginning of the story.
However, unfortunately, Dexter's "winter dreams" are doomed to failure. When he hears of the loss of Judy's beauty, it appears that he himself experiences his own loss of innocence and youth. As Dexter himself says, "That thing will come back no more."