Vodaphone is pretty good and easy. I paid about 500Rs for everything and had about 350Rs credit.. And I still had plenty left by the end (2 months).
Don't be alarmed at the detailed security of buying a SIM card, it's just protocol since the Mumbai attacks. almost 10 years ago
SIM cards in India are easy to buy . You will need 2 pictures of yourself and a passport for security reasons . Be aware that local tarifs work only within a specific area like Gujarat or Rajastan . But anyway using the fone with a local SIM is extreemly affordable .. over 8 years ago