I5 processor

The i5 3750k is good. It'll be nice with a asus sabertooth z77 (although that might be a little pricy) What price range do you mean by "medium cost"?

im assuming by medium you mean not high end but now dirt cheap either. so im gonna go ahead and recommend you the middle:
Intel Core i5-3570K 3.40GHz + ASRock Z77 Extreme4 M Intel Z77 + Gigabyte ATI Radeon HD 7850 OC Windforce 2X 2048M

My budget for motherboard is 120$ to 160$

can u tell how much it may cost for each component that you recommended. Thanks.  

The components bigbang listed will cost around $550-$600 total.

Personally I would opt for a different motherboard, however.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

A little pricier but you can feel safe you'll get the maximum overclock on your CPU.

They are all "good" since they are all off the same production lines. The only one that may require special mention is the 3570k due to featuring unlocked multipliers if you want to overclock. If you do not plan to overclock, you can shave ~$25 off by going for its non-K counterpart for the best performance-per-buck at stock clock.

+1

OP may also consider an H77 series motherboard to save even more money. Though if he would like some more features, Z77 is always an option for him as well.

I am building mainly for gaming for the recently released games like mass effect3 maxpayne3 and so on. But i wont do overclocking and i dont know how to do it either.