What role does Meyer Wolfsheim play in the novel?

Although Meyer Wolfsheim only shows up a few times in The Great Gatsby and we are told very little about him, he plays an important role in the book. The most important role that he plays is indicating that, as Gatsby's friend and business associate, Gatsby did not earn his fortune through honorable means but rather through bootlegging or other illegal actions.
Gatsby wants to be part of the upper class like Daisy so he can win her love, but Wolfsheim provides a reminder that while Gatsby may have the money he does not have the status to be part of her world, since he got his money through illegal activities. Wolfsheim is also Jewish, and as we know from Tom’s racist rant, upper class white people like he and Daisy look unfavorably at association with minorities such as Jewish people. This again reminds us that Gatsby faces difficulties in becoming part of the upper class, partly due to his friendship with people like Wolfsheim.
In total, then, Wolfsheim’s role is as a reminder to the reader that class is defined not simply by money but also by other factors such as the means money is acquired, ethnicity, and religion. Gatsby’s delusion and downfall is the misguided thought that class status is gained by money alone and that he can buy his way out of the class he was born into, and Wolfsheim presence in the novel is a reminder that this is a delusion.