Beforehand, I should point that 'being better than Intel for gaming' is bollocks. It might be better than comparable Intel CPUs at a given situation. There isn't such a thing as a brand being better in every single scenario.
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About your gains, it will depend heavily on which game and with which GPU. In most scenarios you shouldn't be seeing any improvement (as the GPU is the performance limiting factor in most titles/cases), although games as BF4 multi player can see healthy gains from faster CPU clock.