Short answer: List what you need, borrow from friends or libraries where possible and buy the rest second hand or new.
List needs
Write down the exact books you need for the next few months.
Borrow first
Check libraries and friends for books you will use briefly.
Buy the rest
Buy second hand where the edition matches and new where it must be fresh.
Frequently asked questions
Can I sell after exams?
Yes, list them on Bookaao.
Is borrowing realistic?
For short use, often yes.