Chapter 1
Chapter 2 (except 2-1)
Chapter 3
Chapter 4 (except 4-7 and 4-8)
Chapter 8
Chapter 9
Chapter 11 (all algorithms except Isomorphism and Planarity testing)
Note : This is according to 2018 Gate syllabus, might change for successive years.
EDIT : syllabus isn't changed from 2018 so you can follow the above.