Actually, it's possible to overclock your integrated GPU and it will perform good on games that don't use much CPU.
Download Intel Extreme Tuning Utility(Intel.com>Menu>Support>Tools&Utilities>Tools&Utilities>Monitoring>Intel Extreme Tuning Utility.
It can overclock the GPU and the CPU, however I don't recommend this, because as I said if the temperatures reach a certain point, it's gonna slow down to keep the temperatures in check and what you get might be be a better GPU for a worse CPU.
I don't know much about oveclocking, but if you do this please do not raise the voltage before reading a few articles first, because you can fry the chip.
Other than that your warranty is void if the find out you overclocked it.
My guide is look for results of an overclock on the internet and add 20%-30% less then the added clock speed and then start raising it little by little until unstable or you see high temperatures, you need to test in between the raises, MSI Kombustor is a great utility or Furmark, they are basically the same.Both are for the GPU.