India can be done on almost any budget. Ultra-budget travelers manage on $15-25/day: guesthouses run $5-15, a thali meal costs $1-3, and local buses and trains are extremely cheap. The Indian Railways reservation system is excellent value — book 60-90 days ahead for popular routes.
Mid-range travelers ($60-100/day) can stay in comfortable hotels, take AC train sleepers, hire drivers for day trips ($30-50), and eat at good restaurants. Entrance fees for foreigners are often 15-25x the local price at major monuments — budget accordingly. Tipping culture is expected in restaurants (10%) and for guides and drivers.