Gatsby is different from all of his party guests in that he does not drink or socialize and remains a perfect gentleman all night. This heavily contrasts Gatsby from his belligerently drunk guests and foreshadows Gatsby's greater goal and purpose.
In "The Great Gatsby," Jay Gatsby does not appear until the third chapter. From the beginning of the book until then, Gatsby is only seen and discussed by the narrator from afar. At the party, Nick meets Gatsby completely by accident, assuming him to be an odd guest. Nick did not immediately recognize Gatsby because he had expected Gatsby to act more like the type of man who threw such extravagant parties and less like a well-spoken gentlemen.
As the night continues, the differences between Gatsby and his guests become more evident. Nick notes that Gatsby does not drink or dance with anyone, which is odd behavior for someone hosting a party. The only time that Nick sees Gatsby interact with anyone else at the party is when he specifically asks to speak with Jordan Baker. In Chapter 4, it is revealed that Gatsby told Jordan that he is in love with someone named Daisy Buchanan. Furthermore, Gatsby threw his parties and acted in a certain way hoping that Daisy would eventually notice him.