India is by far one of the best locations for photography. Lucky you. North India is very different from Goa. With your itinerary I would recommend spending most time in Varanasi, less in Delhi. Stay in old town of Varanasi. It's likely to be the filthiest place you've ever been, but it's well worth it. Absolutely incredible for photos. A visit to the miniscule Government Bhang Shop is interesting if you're into intoxicating sacraments. But beware: The $0.50 'Opium Bhang Ball' really gives you bang for the buck. But at least in Varanasi it's legal.
The temple called Baba Kinaram Ashram is worth a visit. Pure Indiana Jones type stuff.
Travel rule number one for that country is to pack light and avoid stuff that needs to be charged regularly. Everything you bring will get very dusty many times over if you're not careful. I usually bring my M6 with 35 and 50mm lenses. A wide angle would be nice too, as you're likely to see some beautiful scenery and get crammed into tight places. People let you get close for photos, so don't be shy. And perhaps bring a good P&S like a Ricoh R1 or Olympus Mju for flash and snapshots.
When in India, I buy some amazing 100 ISO Kodak films called Ultima Pro. They cost like $1 and are almost as good as slide film, but I have only been able to find them in obscure places like India and Ukraine(!). Check out the camera market at Meena Bazaar behind the red mosque. I think the nearest metro station is at Chawari (spelling varies) Bazaar. Bring your own B&W, slide and hi-speed film and make sure your stock is full before you leave the big cities. The local B&W film called Nova 125 isn't too bad and very cheap, but quality stuff like Ilford is superior.
Dress conservatively, don't eat with your left hand, talk to people and stay clear of street dogs, especially at night.
Enjoy.