System Requirements for ArcheAge allow to run the game on most PCs. But all power of CryEngine 3 can be seen only on top hardware. Anyway you will be able to play the game even if your computer is not very strong.
Pirates is a playable faction in ArcheAge. Everyone can become pirate after accumulating 3000 infamy points. This guide will help you to join this faction and will give you some valuable information you need to know.