Self taught. One of the reports from people who knew him said he wrote a bunch of software with his own algorithms to help him win at the casinos. You can't really be a professional gambler these days unless you are using technology, which the casinos consider "cheating". He was banned from some casinos that realized he was winning too often to not be using technology.
Education wise he went to a math and science magnet high school. College he got a degree in business administration. But then he went on to be an IRS and a Lockheed auditor, both which require facility with numbers. Don't have to be Erdos for this stuff, but can't be stupid, and have to be smarter than all the other pro gamblers.
Whores he saw regularly said he was a dark and violent guy who paid extra to be able to abuse them.
And it now turns out he did in fact have ISIS contacts and visited them in the middle east.