Honestly, building is still they way to go, even if you know nothing of how to build one. I didn't know anything either, and I easily built my first one within a day of owning all parts. While i is most easily done if you have a friend who has done it before, and if you don't know anyone IRL who has dealt with PC building, use he internet as your friend. Look up PC building guides, talk on forums for advice.
My personal advice on building:
Buy in this order:
Case
Power Supply Unit
Motherboard
Processor
Graphics Chipset
Hard Drive
Disc Drive
RAM
As far as specs go, here are my recommendations (Mind you, I've only done NVIDIA/Intel builds, so I've got no AMD/ATI experience)
Case - You'll want to make certain that your case has a decent airflow, more fans/larger fans = better. You'll also want to make sure it is large enough for your needs, supporting an ATX or E-ATX motherboard.
PSU - Most modern PC builds will require a 750-1000W PSU, and you'll want to pay attention to reliability with your PSU, as they are the most likely component to fail (in my experience). Keep track of your PSU requirements on your GPU, CPU, fans, sound card, etc...
Motherboard - This requires the most thought put into compatibility. You'll need to pay attention to how much RAM it supports, what kind of RAM it supports, what kind of processor it supports, # of PCI slots, etc...
The motherboard is easily the main thing you'll want someone who is knowledgeable to help with
Processor - You NEED a multi-core processor for modern gaming, preferably a quad Core, and you'll want at least 3.1 GHz for dual core, 2.6 for quad core.
Graphics - Nvidia 200 series recommended, don't know much on ATI.
Hard Drive - Recommend over 500 GB.
Disc Drive - A fast DVD drive. Blu-ray isn't required for PC gaming, at least not yet.
RAM - DDR2 or DDR3, whatever your motherboard supports, but if you currently don't have a motherboard selected, I recommend DDR2 for now, because DDR3 is still somewhat unstable, although in the future there may be a greater push for DDR3, but there currently is no real reason for it, because it costs about 3 times as much as DDR2. 8GB recommended.
Also, if you have/want a fancy sound setup, you'll want a sound card, but onboard sound generally works well enough, unless you insist on hearing every footstep in full 3D audio. Mainly helps in online FPS games. Will add to PSU requirements.
Networking card - Do not get, do not need, unless your Ethernet port is broken, or you really feel the need for internal wireless networking capabilities.
Also, you'll want a DVI/HDMI compatible monitor, VGA simply doesn't cut it.
Keyboard and mouse are up to you.