A medium performance, budget gaming pc?

i have been looking around the internet and on websites like www.dinopc.com for a pc that could handle games like call of duty zombies custom maps and day z on a similar level to xbox/ps4 and i have a budget of 300-350 pounds and i would be willing to make one but to be honest i have no idea as i have generally only played pc games on my laptop is it as easy as most of it clips together or will i have to get into soldering and all that jazz so could someone:

A: link me to a couple of decent 300-350 pound budget pc's

B: give me a brief knowledge of Gaming PC building

C: link me to parts to build one

D: improve my knowledge of gaming pc's

and i am hoping to get it built by Christmas so would i have to buy all the parts at once or could i buy them as i go along building it.

this is my first post on here so any and all tips would be appreciated.

Tip #1: Please make hardware related posts here from now on

Tip #2: All you need to build PC's is patience and the willingness to follow a simple guide on the internet (which you can print out or read on your phone). It all clips together.

Unfortunately I don't know the best sites in Europe to buy PC parts from, so I probably can't help you there.

Do you need just a tower, or do you need monitor, mouse, keyboard, etc?

http://uk.pcpartpicker.com/p/tDxjMp

Should do the trick

@KHAndAnime: ok sorry also i need the whole thing monitor gaming mouse keyboard all of it and ive been reading up a bit on making one and my biggest fear is getting the wrong cpu for my motherboard or something