To buy a pearl necklace
For a mistress? Nick may be using his cynical imagination here.
Or perhaps this necklace is for Daisy? Daisy had been “bought” with a $300 pearl necklace from Tom before they were married. Or, maybe Tom is trying to make up to Daisy for his past/ongoing affairs.
Either way, this line points to how Tom continues to hide behind his immense wealth to pass his time and solve his problems.
To help improve the meaning of these lyrics, visit “The Great Gatsby (Chapter IX)” by F. Scott Fitzgerald and leave a comment on the lyrics box