Tax saving option for freelancers

Hi,

     I am working as a freelancer for a start-up. My invoice has both project fee and GST (18%) mentioned. I collect both of them and pay back GST every month. Need clarifications on the below:

1. Should I calculate my gross total income is (Total payment - GST) ?
2. My Gross total income from the company is expected to be ~48 lakhs. So can someone please suggest better options to save Income Tax?
   1. Subtract business related from expenses(Salary, rent, travel, etc.,) from the Gross total income and estimate the taxable income.
   2. I heard that there is an option to declare only 50% of Gross total income as taxable income. Am I eligible for this?
   3. Should I estimate both of the above and choose one of them. Or Is it possible to avail both the above - business expenses deduction and 50% exemption benefit?

Thanks in advance.

Thanks

Mani