[Logic_]

Most games won't even use all your cores. What your main aim should be buying the fastest memory, GPU and storage drives! Remember that games are now requiring more processing power and you need a fast enough processor that can handle your graphics card so you don't suffer from bottlenecking. CS GO don't even require much GPU or processor power and generally all Source engine games are poorly optimised same as the new CS GO maps.

Reddit PCMR has answer to all your questions!