Hi Mehak, Welcome to the Capital of India. You would surely enjoy the place.
I haven't heard of hostels much in Delhi. Still try looking at Zostel or Hostelworld app. Otherwise you can easily book an Oyo near CP as Connaught Place is the central hub to visit the entire Delhi. There is metro available and the station name is Rajiv Chowk. Roam around the CP circle at night, go for shopping, try new eateries or pubs. Take a metro, get down to Chandni Chowk and enjoy the place by travelling on foot. The place is famous for designer clothes at affordable prices, parantha wali Gali, natraj chaat house, lassi or falooda at giani and much more. If you eat non veg, take a rickshaw and head to Jama Masjid and try Karims, Aslam Butter Chicken, Qureshi kebabs and lots more. For Hauz khaas , you can get a metro easily. There are good pubs and a deer Park. Try out with the one having ladies night and enjoy the crowd over there . Have fun! Wish you a pleasant stay.