In many respects, Nick ends up "meeting" a part of himself. Nick ends up meeting the people already specified in terms of the Buchanans and Jordan Baker. More importantly though, he begins to associate himself with this world of wealth and privilege that proves to be alluring to so many of the time period. This world of social exclusivity and one where an individual's value is highly determined by the size of one's wallet and bank account is what Nick ends up "meeting" in the first chapter. Through conversation, Nick also ends up "meeting" Gatsby, the legend surrounding him, and helps to develop a dual consciousness between what he knows of Gatsby and what will happen when he ends up meeting him later in the work.
If by "meet" you mean "is introduced to," then Daisy and Tom Buchanan do not figure in since Nick is a second cousin once removed to Daisy and he has seen her before. Likewise, Tom Buchanan is familiar to Nick, as well. Nick states,
I'd known Tom in college. And just after the war I spent two days with them [Daisy and Tom] in Chicago.
Interestingly, however, Nick does remark, "I drove over to East Egg to see two old friends whom I scarcely knew at all." This line is very telling as it indicates the observant quality of Nick, who notices that the former football player now dresses in riding clothes and boasts of what he owns.
As he is led by Tom into the house, Nick notices two young women: "The younger of the two was a stranger to me." The girl who has her chin raised "as though balancing something on it" is Jordan Baker, who remarks to Nick with contempt, "You live in West Egg....I know somebody there." She then introduces the name of Gatsby, whom Nick has noted earlier in the chapter as his neighbor.
When Nick returns to West Egg and his house, he sits for a while in the car which is under a shed; he notices that fifty feet away
a figure had emerged from the shadow of my neighbor's mansion and was standing with his hands in his pockets regarding the silver pepper of the stars. Something in his leisurely movements and the secure position of his feet upon the lawn suggest that it was Mr. Gatsby himself, come out to determine what share was his of our local heavens.
Nick decides to call to him, but Gatsby has vanished, leaving Nick again alone in the "unquiet darkness." So, while Nick has encountered Gatsby, he has not yet met him.
In this first chapter of The Great Gatsby, the exposition introduces the reader to the somewhat unreliable narrator, Nick Carraway, who presents the contrast between the wealthy socialites of the East Egg and the nouveau riche of West Egg, who are not as "acceptable."
Nick Carraway meets a bunch of people in Chapter 1. The most notable of these people are the Buchanan family and a friend of theirs. The Buchanans are named Tom and Daisy. Their friend (more of Daisy's friend) is a young woman named Jordan Baker.
I suppose technically he does not meet Tom Buchanan. They had known each other in college as well. And he had known Daisy before -- they were distantly related. So I guess the only real character he meets is Jordan.
Daisy ends up being one of the main characters in the book. Jordan Baker and Nick end up having an affair.