Because CentOS is the free version of Redhat Enterprise Linux (RHEL), it does not come with any support by default, like you might expect from RHEL. That said, there are many third parties who are capable of supporting CentOS. Your hosting provider can certainly provide support for you, or if you need additional assistance, you can always contract with one of many third party management companies.
A gaming server is a dedicated server used for online games such as World of Warcraft or Minecraft. The benefit of a dedicated server for gaming is that your server is often more stable than the game client itself, which is impacted by multiple players and resources. For a smooth gaming experience that you control, a dedicated server is the way to go.