The novel opens with several ambiguous statements about Gatsby:
Only Gatsby, the man who gives his name to this book was exempt from my reaction--Gatsby who represented everything for which I have an unaffected scorn.
And later, Gatsby is described as having an "extraordinary gift for hope, a romantic readiness such as I have never found in any other person and which it is not likely I shall every find again."
Then we learn that "Gatsby turned out all right at the end" but that there was "foul dust" that "floated in the wake of his dreams."
In these opening statements about Gatsby we learn that Gatsby was a dreamer, an optimist. He is one who is different from the rest of Nick's acquaintances, and that even though he possessed less than admirable qualities (for which Nick had unaffected scorn), he ultimately was all right.
These references are somewhat vague and paradoxical, but we are intrigued by these statements and alert when we find out that the mansion next-door to Nick's is Gatsby's. We are well aware now of the fact that Gatsby is very wealthy, but by the end of the chapter, Gatsby becomes a figure shrouded in mystery as he stands upon his lawn looking out to the bay "hands outstretched" toward the "dark waters" and the green light across the water. This mystery was earlier alluded to when at the Buchannans' Jordan mentions Gatsby's name, and Daisy repeats it questioningly, indicating some connection that Gatsby may have with Jordan and possibly with Daisy, connections later confirmed by the events of the story.
I think that we learn much of the social setting that Nick is entering from the first chapter. Through the first chapter, we learn about East Egg and the Buchannans and the Bakers who will dominate the rest of the narrative. The impression we get of Gatsby is more of the social setting in which he is immersed. When we see Nick looking at Gatsby, alone, on his own, and standing apart from all else, it is an indication that he is going to be different from the others around him. The impression we derive from this is that Gatsby is "alone in a crowd," and Nick's impressions of him concur with this. When the opening lines of Nick's narrative validates the idea of "people not having the same advantages," it is a call that resonates at the end of the chapter when he sees Gatsby for the first time in a different light from the others in East Egg.