Goa is the best place in that particular time
and thus your budget is very high you can easily find good accommodation and other things like travel and all
Manali is also a good option for camping n all but the way you can enjoy in goa i guess you cannot in manali plus the budget will be little hard to maintain plus in Manali it will be too cold now
And you will get to enjoy the fullest and you will get to see new year celebrations, casino pubs shacks and many more
seriously Goa is the best place for that budget
I would recommend that goa is the best place to visit in december. You will definitely enjoy nightlife, beaches, food of Goa. Travel in group is very cheaper in goa.
With this budget and considering a girls group we have number of options here! 1. Goa
2. Andaman (If well planned)
3. Spiti 4. Himachal - Major Towns & Cities
5. Leh Ladakh 6. Darjeeling
7. Tawang
8. Munnar - Kerala
9. Uttarakhand(Plan with India Hikes)
In this budget you can easily cover the three hillstations: dhanaulti, mussourie and dehradun in uttarakhand all of which are very close to each other. This time of the year, it is most probably that it would be snowing, which could be hell of a view to see.
Christmas is the best time to be spent in North East. Plan a trip to Shillong. Make early reservations at the Hotel. There is one Boutique hotel also by the name of The Habitat. Other than hotels, ample homestays are available. Reaching there is quite easy too. flight to Guwahati and then you can either hire a cab or book a self drive. drive is amazing. you can take a small halt at Badapani.