you need to actually give your graphics card.
You stated one of two different manufacturs. That really only narrows it down to about a hundred or so, and then you also have the aftermarket cooler/manufacturs like asus, evga, msi, ect. But that wont matter much.
Overclocking your processor isn't going to yield any major fps gains. That's strictly gpu, unless your cpu is bottlenecking which on most games there shouldn't be a reason it would. Your also going to have to make sure you have a good cpu cooler, and case fans providing good airflow if your going to want to overclock. Your also going to need to make sure your power supply is good enough for an overclock.
There are also several tutorials here on toms, and hundreds more if you google overclocking your chip. Its all hit or miss, as no two chips are the same. Motherboards also overclock differently.