It depends on your interest and your budget.
In North India you can visit Shimla, Manali, Dharamsala, and go for some treks.
Else in South India you can go to Goa, Coorg, Mysore ,kerela, Pondicherry etc.
If you can make to Western ghats it will be dream expedition for you. During monsoon these ghats gets lushed with greenery and you will witness some extraordinary scenes. You can do trekking in Lonavla like Lohgad qila, visapur trek, Rajma hi Trek(my favorite), Ghangad fort trek, kalsubai trek(highest ranges of western ghats)
If you have time like 8-9 days and a good budget like 30-35k than i would suggest go and explore Laddakh..everyone should visit Laddakh once in their lifetime...if you already been there than Spiti or Bhutan anyone you can choose...