What is best or cheapest at the Home Depot store in San Carlos, California, will not help you much in whatever city you're in in India.
Also, "best" and "cheapest" are typically mutually exclusive -- pick one!
If I were you, I would go to the store you'd shop from, and look at the cordless drills/screw drivers, and buy the one you think seems appropriate.
If you're doing mail order, then you can do the same research online from the store/stores you'd consider buying from.