Ragefest of emo kids mostly. But finding a competent guild can solve most (not all) of this.
Mesos are the currency used in the game.
You can win without using money, but it's much harder now due to a system called MTS being removed. You can indeed pay to win though.
OP class is usually whichever is the newest, balancing is almost nonexistent in the game.
PvP isn't that great and a recent patch has removed it for the time being.
You don't.
Go where?
In honesty, unless you have a solid reason to start/play (friends), I'd suggest looking for a new game. The game's concept and patches come from Korea and are actually really good, however the company that runs the game is the worst I've ever encountered. I have an unanswered support ticket of 3 years so far, the customer support is awful unless it's about you trying to use more money on the game. And item balance and fairness are thrown out the window for more profits whenever possible.