Japanese Park (Rohini) is a good choice.
Visit gardens like Garden of five senses, hauz khas garden, Okhla Bird Sanctuary and many more famous gardens.
Humayun's Tomb or Safdarjung's Tomb
Nehru park, punjabi Bagh park(west) ,budh Garden
Nehru park, punjabi Bagh park(west)
Japanese park and lodi garden