Although keen observation and awareness of your surroundings are all that is needed for birding, the joy of birding can be greatly enhanced with a few tools.
The most important item is a good pair of binoculars. Binos come from around Rs.3000 to over a lakh or more. Reasonable binos can be bought by amateur birders for about Rs.3500 to Rs.5000. This is the most expensive item in a birders kit.
A field guide is a must, for quick reference in the field. A good guide can be bought in most major bookshops, for about Rs.500 or less. This is all what is absolutely required for starting bird watching.
Other small things can help: backpack, water bottle (for long days in the field), a logbook (to note down your observations), good (trekking) shoes.
You can also buy: spotting scopes (a terrestrial telescope with high magnification), birders jacket (with pockets for most of your stuff).
Bird photography is different from bird watching, although several birders also take photos.
Equipment is a long term investment...your binos, if used carefully, should last for years.