Help me pick out parts

So my current pc is not that great and im planning on upgrading it. My current specs are:
GT710
FX4300
8GB Ram
450W PSU
GA 38lmt usb3 r2 mobo

I am planning on having a budget of 200£ on upgrading these specs. Terms of compatibility wise I only want to upgrade the gpu and cpu. Nothing else. I have many GPU's on my list but I need someone to pick me out a good gpu and cpu combo for playing games such as Overwatch, Rainbow six etc.
 


Any specific Cpu and Gpu which is compatible? There may be used items on the market but nothing too powerful as most of my parts will probably not support it