For UPSC optional subjects, aspirants should prioritize comprehensive and standardized study materials. Core textbooks recommended by the UPSC syllabus should be on the top of the list, alongside reference books for deeper understanding. Additionally, aspirants may use previous years’ papers to gauge the type of questions asked and the depth of understanding required. Joining subject-specific forums can provide insights into essential topics and current trends. Moreover, using study guides from reputed coaching institutes may help in consolidating knowledge effectively while balancing the time constraints of UPSC preparation.