my budget is about 300 pound i already have the graphics card (amd radeon r7 240 sapphire 2gb) i also prefer amd cpu's i am going to use this pc to play games like hl2 and dota 2,
if you need to know anything else just ask
I think you would be ok with an r7 260x -> http://uk.pcpartpicker.com/part/sapphire-video-card-1003662l
For the games you want to play your gpu would be sufficient and the rest of the system... well overkill. I just suggested a better card so that you can play some other modern games too. If you are not interested in that dont spend extra money.