What CPU should I buy ?

What kind of games are you considering playing? If you're going for low-end games that aren't demanding, like pinball, then almost any cheap processor will do. For video editing, you'll want several cores. AMD CPUs have the advantage of being cheap and powerful. Thus, consider at least a dual core. If you can find a great Black Friday deal for a quad core, go for that instead as it'll make both gaming and video editing more effective. Changing CPUs is generally a time-consuming process as you generally get stuck having to buy another motherboard.