such games like : Minecraft/SAMP/CS/Dota and other games? Also if its not that good can you guys suggest other ones since i srsly want a good GPU 
If you will only play those games , then :
MOBO : Gigabyte GA-970A-UD3P AMD Socket AM3+ Motherboard ( This MOBO for AMD FX 6000 Series , It can run all new GPU , it has crossfire option as well so you can have 2 GPU's or a GPU which has crossfire)
PSU : 500W+ ( recommended , incase you need to upgrade)
CPU : Intel I3 Processor or AMD FX 6000 series
GPU : AMD Sapphire HD7750 / 7770
RAM : 4GB DDR3 800MHz (minimum)
HDD : 320GB-1000GB (recommended between 500-1000 @7200RPM for max performance)
The MOBO : 70 Pounds
The Processor , Im not sure about the I3's price but the AMD FX 6300 will cost you 70 Pounds.
The GPU will cost you 70 Pounds.
The price for the RAM will be different according to what brand and MHZ you buy.
HDD : According to size , speed and RPM.
PSU : EVGA 500W 80 Plus Power Supply 30 Pounds.
Good Luck.