In Chapter 2 of F. Scott Fitzgerald's The Great Gatsby, a few different social classes are definitely present at the party held in Tom Buchanan and Mytle Wilson's New York apartment. We can see class distinctions portrayed through descriptions of the characters, especially through descriptions of their manners.
Mytle Wilson and her sister Catherine represent the uneducated working class. We know Myrtle is from the working class because her husband owns a car garage. We can tell her sister is equally uneducated due to the fact that her makeup is described as having been done poorly. For example, her complexion is "powdered milky white" and her eyebrows are described as having "been plucked and drawn on again at a more rakish angle." A woman of true class would do her makeup more elegantly and much more subtly.
Mr. McKee, as a successful photographer, represents the more skilled middle class. Though being of a hirer class than Myrtle, it's clear that he too is not a gentleman due to the fact that he shows up for the party with a spot of shaving cream still on his cheekbone. In addition, his wife is clearly still from the uneducated working class, as we can tell by her manners. She's described as being "shrill, languid, handsome, and horrible."