The character Meyer Wolfscheim of The Great Gatsby certainly calls to mind the legendary Meyer Lansky, also a Jewish mobster and a giant of the underworld who was so clever and cautious that he never went to prison and died at the age of 80. Like Lansky, Wolfscheim was involved in racketeering which can encompass many illegal acitivities, such as gambling, prostitution, trafficking and interstate transportation of stolen goods, money laundering (hiding illegally gotten money from the government/IRS), bribery, tampering with witnesses, retaliating against witnesses, murder-for-hire, fraud.
That Wolfscheim was involved in murder is evidenced in Chapter Four and by his molar cufflinks. In addition, he is almost paranoid about being killed himself. In Chapter Four, for instance, he drinks his coffee with a jerk and gets to his feet quickly,
"I have enjoyed my lunch," he said, "and I'm going to run off from you young men before I outstay my welcome."
Wolfscheim is also afraid to appear at the funeral of Gatsby as funerals are often where FBI seek mobsters.