Why was Mr. Meyer Wolfsheim's role so important in The Great Gatsby? How did it affect the story of the movie?
I am not acquainted with the book myself. But as far as the movie is concerned, it is not expected to be known much about Wolfsheim.
Wolfsheim is a friend of the Gatsby. He is a member of New York's underworld. He also fixed the 1919 World Series. He was in some sort of "bond-scam". Further, Wolfsheim gave some hints to Nick that seem to indicate that Gatsby, who always tried to beat his own drum in front of the public by throwing parties and all, was merely an associate of the former and Wolfsheim carried much of the later's expenditure in order to carry on with his own business making Gatsby a mere carrier of his interest. As The Washington Post describes-
Wolfsheim seems to be using Gatsby for retaining his own anonymity and he might as well was funding fir the parties to get familiarized with the high-society. Although, the sponsor can the Gatsby too; this remained a mystery.
So as a character, Wolfsheim was not that important, but he let us know some true facts about the Gatsby, who apparently could not be believed easily regarding his business profile.