Fitzgerald has delayed the main appearance of Gatsby until this chapter, the reader has seen him from a distance and also heard things about him from Catherine (late in chapter two) but it is only now that we meet him. Fitzgerald uses a variety of methods to introduce Gatsby and the mist that surrounds him; at the start of the chapter there is music in the distance from the party at Gatsby's mansion, this could also be a metaphor for the fact that Gatsby is always very distant, he is never in the thick of it; he is portrayed immediately as being quite mysterious, and the distant music helps to outline it.
Another "theme" of this chapter could be wealth. The random guest's that find their way to his door don't even know him, they exploit his riches and wealth, "at weekends his Rolls-Royce became and omnibus" literally a bus for conveying people to and from his parties.
The way the guest's use his facilities, "I watched his guests diving from his raft or taking sun on the hot sand of his beach while his two motor boats slit the water of sound," the excessiveness of it all, the fact that he has two motor boats, his own private beach. Later on Fitzgerald talks of a machine that juices the oranges and lemons and that all you have to do is keep pressing a button - the simplest of jobs - yet Gatsby still gets the Butler to do it, it illustrates his wealth and upper classiness. Again later on the vastness of the orchestra that he gets, "no thin five piece affair, but a whole pitful of oboes and trombones and viols and cornets......" the list demonstrates how vast the orchestra is, and at this point here,