I've built several over the years and for a while did it as a business. Maybe I've just burned out over the years, but I find it's only worth it anymore when you need certain specs.
With what you want to do (gaming, video editing) it will likely be worth it, because you're likely to want certain things in the hardware department. If it was just for email, word processing & web surfing I'd probably just grab something stock. It's not at all difficult to do and there are several tutorials to be found online (some with video) if needed.
Sometimes places like
iBuyPower and
CyberPowerPC have some pretty good deals on gaming systems depending on what you want for a setup. Never bought from either one, but have heard OK things from a few folks.