Throughout Chapter 1, we read the story through Nick Carraway, the narrator of the story. We get to see how he sees things, and what he thinks of all the other characters. In the first chapter of the book we see Nick as quite an interesting narrator because he first seems reliable but it seems as we read further that he is seeming more unreliable.
For example a hint to Nick's true moral character is given on the first page of the book when he misunderstands his father's advice. His father said, "Whenever you feel like criticizing anyone just remember that all the people in this world haven’t had the advantages you’ve had.” And so following this advice Nick doesn't seem to ever pass judgement on people and therefore he never relies on his first impressions as completely accurate.
Nick is invited to a dinner party at his ‘second cousin twice removed’ Daisy’s house. He's then introduced to Jordan Baker - and while he finds her attractive, in the same thought, he knows she will never be someone with whom he could maintain a satisfying long term relationship. Based on the advice his father gave him as a kid, this characteristic is completely mindful. As a narrator - he tells us exactly who these people are, but because he's so likeable and nonjudgmental of everything, they end up trusting him.
"Most of the confidences were unsought." What Nick is trying to say here is that, for reasons he cannot understand, people feel comfortable telling him their innermost secrets. People are always opening up to him. He doesn't ask for it. He certainly doesn't put himself in situations to receive it - but it just keeps happening.
Nick is one of those all around good natured, but somewhat quiet individuals. He doesn't do a lot of complaining. He probably enjoys having a good time but is never the life of the party. In the world of materialism and richness that he is part of he is not very materialistic. He is not an attention seeker in any way. These are the small but important details that make people trust and open up to him - and make him a reliable narrator. He calls things like he sees them, he is smart and experienced, but deep down, and nothing really bothers him.
On the other hand, Nick seems to be quite condescending and thinks he is better than others. He feels cozy and superior in his strict Midwestern values taught to him by his father. The fact that he is always ready to make exceptions for others and not judge others, means that he thinks he is better…