Yakuza aren't that widespread. If you want to see a pan-international group of mafia, the Chinese triads (Cantonese-based or Fujian/Taiwanese-based) are always the huge ones.

Do they run gambling rings? Im think gambling is illegal in Japan at least for money.

Illegal by law. By practice, it's quite popular esp. with Pachinko (mostly run by Koreans living in Japan).

I know about pachinko where people trade items at other locations for money. Dose the yakuza have a hand in that??

Used to, but from what I understand now they are mostly Korean owned nowadays.

So from what im getting they are bussiness men that work illegally but just as a starting place to get customers? but they aren't violent anymore?

I don't think it's that simple. There are all sorts of yakuza, and chances are anyone who brags about it probably isn't one, but the deepest members look like the most normal people in Japan.

is yakuza really rich?

When were they ever so violent? Or do you watch too many yakuza movies?
The good ones (:D ) will never even touch amateurs like you and me.

Yakuza: Japan's criminal underworld - Google Books

i just read this. they sounded pretty violent. lot to think about