If the capital gain would be LTCG, then you would have saved all your gains by investing (i.,e by purchasing) a residential house as per section 54F.
Since it is STCG, you are required to pay tax @ 15%. If you over annual income is less than exemption limit then you can set-off the balance of exemption against capital gains earned and balance has to be paid @ the rate of 15%.
You can give donation and for the same you can also claim as deduction as per respective section.
This is my opnion and please do consult a professional before taking any further step who will help you out better than me.
Regards,
Harshal Vora