Overclocking 7770 and best settings

Anyone?

well you can push your 7770's core clock to around 1200 mhz and the memory clock to around 1500mhz without much fuss...but do keep in mind that all cards don't oc to the same levels some may be more while others less.
don't forget to stress test your card after the oc and keep a watch on the temps.also do not go on to playing with voltages unless you are sure.do keep in mind that you are new to this and so never overdo anything.

all the best.

Well I suppose it would depend on the setting what would be the best settings to change there are settings like terrain detail or draw distance or Anti-Aliasing and Anisotropic Filtering which will filter and smooth out objects. These are things you will probably want to do on your own to get a feel for what looks best to you. However keep in mind that you have a entry level card and maxing out most games will not be possible for you.

In terms of overclocking I agree with Sid its more of a luck of the draw sometimes you have a chip that is more resistant to heat and you can push it a bit further. And yes pushing your GPU beyond its limits can shorten the life of the card.