Need help on PSIR preparation.

Hello everyone first time posting here. I recently started my upsc preparation, though I am from economics background i am opting for PSIR. I finished studying chapter 1 Part 1A of PSIR syllabus from Gauba book last night and it was fun but I'll need some time to digest what I have read. My doubt is on the syllabus regarding the names of thinkers mentioned in it and the topics, do I stick to the names mentioned in the syllabus or go beyond that. Same for the rest. Can a senior please help clarify? Thank you.