Mario Junior :
how useful is overclocking when it comes to gaming like bf4 like intense gpu and cpu games?
It really depends on the game. Here's something I didn't know until I observed it through my own CPU overclocking and someone confirmed it for me on here:
When you overclock your CPU, for GPU bound (not to be confused with GPU-bottlenecked) games your graphics card actually receives more leg room to work within so those games will likely perform noticeably faster. For CPU bound games, surprisingly enough, even huge overclocks may
not do much at all. You'd think that it'd work the opposite way; CPU bound games would theoretically receive massive increases from huge overclocks but no. From what I understand, it's because CPU bound games may run slower because of latency issues which, even after overclocking, still remain. Meanwhile, I've had confirmation that on the more GPU bound games that are CPU bottlenecked, there's been performance increases of 13 fps for a 1.0+ GHz Overclock.
So if you're expecting to get a huge increase in performance through overclocking for games like Skyrim or Borderlands 2 which are both CPU bound, I can already confirm through personal experience that it may not do much, assuming your GPU isn't bottlenecking you for said games. However you may get a huge increase from other games.
As for GPU overclocking, I can't comment unfortunately because the one time I tried to OC my GPU I crashed. Guess I wasn't stable. No harmful effects though.
But on to why you should actually overclock: It's fun and it's free and it means a potential performance increase. Don't worry, damaging your equipment is hard unless you severely overvolt, and it's actually pretty easy to stay within the limits of your CPU's voltage. Just take voltage increments up by 0.025 at any one time and you're safe and with any CPU never exceed 1.55V.