Article claims he moved to NYC in 1988, looked him up, he is apparently a writer and he's just released a book (fiction) on the mafia called "The Vindicators". You can read an excerpt from his novel here:

http://www.clublighthousepublishing.com/productpagem.asp?bNumb=388

It's pretty bad. His publisher's website also looks like it was built in 1998. Looks like a guy just trying to trade on the name Gambino and get some publicity for his book. I like how the article makes this claim:

"Giovanni has fostered relationships with major movie producers, and he is on his way to building a highly respected career in Hollywood"

lol, sure he is. I'd be interested to know who his father is, though.