The X3100 is pretty crappy and you'll only be able to run old games with it. First-person shooters are basically out of the question. In fact, pretty much any 3D games are out of the question except older ones like Warcraft 3, Quake 3, or Unreal Tournament '99 (the original, which is Windows only).
Basically, if you want games, you'll have to get something else to run them. Either a console or a gaming PC. Your MacBook will not be able to handle many at all.