Places to visit mein - obvious ones I'll skip (Humayun's tomb, hauz khas fort, exploring old Delhi, etc) Slightly less obvious ones that are all near metro stations:
- Feroze Shah Kotla (the ruin not the stadium) and khooni Darwaza
- Bijay mandal/begumpuri masjid/lal gumbad/chor minar
- Mehrauli Archaeological park
- Coronation park (though it's quite decrepit rn but still)
- Bara Lao Gumbad
- Sanjay van forest/jahanpanah forest
- National museum/NGMA/Triveni kala sangam
There's a guidebook by Lucy Peck on Delhi that is great for lesser known places/hidden gems. You can combine that with any of the good books written on Delhi to get the cultural mix with it also.