1.This moment is important because it's almost like Gatsby had a certain interest in Nick. He was the only one who got an actual invitation to the partyso it definitely makes it seem like Gatsby knows who Nick is without ever meeting him before. A lot of people don’t even know who Gatsby is, they simply just go for the party and being able to say they went to a Gatsby party. Some were introduced but even then they still just kept going on with the party so maybe it could just be because Nick is his neighbor but there still seems to be something more to this situation.
Quote 1 means that sometimes, there are those at the party that Gatsby hosts, who haven't even met Gatsby. They are at the party because they want to go to this no-invite fancy party that this rich guy is hosting. They just want to go out and they have no interest in finding out who the host actually is. They'd rather make up their own assumptions and get on with the dancing.
Quote 2 is said by Lucille, a party-goer. What she means is that she doesn't care what happens or what decisions she has to make as long as she is having fun. She just wants to forget the consequences to everything and have a free for all.
