Acc. to your needs, my suggestion would be AMD A8 3870K (Rs. 6000).
Yes, the Mobo Gigabyte A55M-DS2 (Rs. 2700) is good enough for a budget build, if you don't want to do extreme overclocking.
And, you will be fine with the stock cooler, even with mild overclocking.
Thanks a lot for your suggestion Vinay, I suppose you are from India too, can you help me out about from where should I buy the following items. I am from Chennai and I am comfortable buying online too.
AMD A8 3870 costs 6700 on flipkart and about the same in the shops at Ritchie street, where can I find it at 6000? Also the mobo costs 3400 online and about 3200 in the local stores, where can I find it for 2700?
Thanks again mate