Passage 2
"In the main hall a bar with a real brass rail was set up , and stocked with gins and liquors and with cordials so long forgotten that most of his female guests were too young to know one from another. "
In this short passage Nick already gives the reader a good overview of the "real" 1920's:
They are shaped by plenty of excessive illegal parties (of course alcohol belongs to a party; otherwise it would be a child's birthday-party) and it obviously becomes even better by the attendance of young, beautiful women ("female guests were too young"). Because of his choice of words (--> they were too young to know one from another), Nick subliminally ascribes them to be verdant and maybe even that they are solely interested in the (money of the) businessmen who attend the party.
Furthermore Nick seems to be very impressed by the main hall because some drinks are "so long forgotten" that they are probably very rare & valuable because of their age.
