laptops for gaming

So i need some help. I work away alot, and usually game on console. Im looking at buying a laptop for gaming while im away, but dont know what specs i should be looking at, or what im looking at in general. Travelling by plane i dont want anything overly heavy. It would mostly be playing FPS type games. Im not looking to spend alot of money. Would a laptop costing around $400-600 with 8gb of ram be enough?.

Also, thoughts on buying a second hand gaming laptop?