Fitzgerald illustrates the parties by going into depth with descriptions about the location and setting, the preparation and activities as well as the type of people who attend. This demonstrates to the reader that the location was specifically meant for daisy as their homes are opposite to each other, Gatsby has hope that Daisy might see the party and come over. The description of the activities and preparations just show the reader how extravagant the parties are and symbolises his wealthy he is. In addition it also shows that the parties are massive as they have many days of preparation and large quantities of oranges etc. the different types of people attending further emphasises how big his parties and how well known they are. I hope this helps!!