Hey there,
u have a decent graphics card I found it to be the equivalent to the gtx 960, I don't think it will struggle playing minecraft or BO3.
do you know what mother board u are going for? socket wise? once you do u can pin point which cpu will work with it. The Standard (priced ) mobos atm are 1150.
a lot of retailers are doing motherboard and cpu bundles. some even come with ram too. I have seen some for £300 on maplin. or amazon. lol
ur case wont matter to much tbh. Just get a standard ATX chassis. your gpu is fairly large and u want to have the room for it.
If your gna overclock, ( as you have an OC card) you will wanna grab the components built for over clocking. so a cpu and motherboard also capable of doing so.
The biggest thing id say not to cheap out on, is you PSU. This badboy is gna be keeping everything in your Rig running.
I would spend minimum £70 on your psu and nothing below 80 bronze 600w. Get something shitty and it gives out and it takes your mobo or anything else sometimes triple its worth with it.
you could very easily build a decent little rig for this money. heres what I personally would go for :
Excluding GPU, Case and OS.
your optic drive ( dvd tray ) is something I wouldn't go pricey simply because the only time I ever used mine was for OS and software install, I took it out because ......... just because lol
I just made this based around ur gpu.
https://uk.pcpartpicker.com/parts/partlist/
have a look, spend alittle more and get an SSD if you want fast loading times and stuff.
hope this helps either way. tried explaining it in a way I would have understood some many years ago lol