What is us onsite salary for C3B?

How much can we save as a single person post tax and expenses?

Depends on mindset.
Example: Low expense cities: somewhere between 2.5-3 lakh per month savings. At least 2lakh easily.
It can be increased by: Do trips but plan well to find deals.
Shared accommodation can increase it instead of living alone in 1bhk.
Take sensible car like Honda, Toyota and save on gas and maintenance.

Gross India salary will be saving?

Monthly net will be saved + Indian taxes also be saved