What Role Do The First Lines Of The Great Gatsby Play?

The Great Gatsby is the quintessential Jazz Age novel, capturing a mood and a moment in American history in the 1920s, after the end of the First World War. The novel has been highly praised for its prose style, and the deft way Fitzgerald handles the voice of his narrator, Nick Carraway.
The first chapter of the novel begins with Nick’s narration:
In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since. "Whenever you feel like criticizing any one," he told me, "just remember that all the people in this world haven't had the advantages that you've had."
The first thing these lines show is that the story is going to be told in the first person (meaning it's narrated by an " I" voice who is a character in the story and who is present at the events he describes).
The second thing the readers see is that there is at least one time shift in the narration. Nick is older now, but is looking back on youth and a more "vulnerable" time. There are several different ways to interpret this vulnerability, especially before we have read further: this narrator may be vulnerable to being hurt by others, to being influenced by bad surroundings/people, or maybe even to taking his dad's advice at face value.
From the opening lines the audience also gets the first clue into Nick's background: he comes from money, education, and breeding (" advantages" ), which will allow him to fit in reasonably well in the old-money East Coast world that he will encounter in the novel.
The readers discover that Nick has had a hard time connecting with his dad's advice. The "advice" from his father seems really more like a dig at Nick. The phrase "whenever you feel like criticizing anyone" makes it sound Nick often judges other people's behavior and actions without considering context or circumstances. This shows one of his main weaknesses - and it's a pretty significant one considering Nick is going to be the eyes through which the readers see all the other characters. Primarily, this "advice" puts a big barrier between Nick and "all the people in this world" because he has had "advantages" that they haven't. This means that during the rest of the novel, this snobbishness and this tendency to dismiss everyone else as being inferior is something to watch for in Nick's description of other people and events.