Short answer: Confirm your college book list, buy one core textbook per subject, and use seniors or second hand copies for the rest.
Start with your list
Your college or faculty will usually recommend textbooks for anatomy, physiology and biochemistry. Start there, and add other references only when needed.
One core book per subject
Multiple textbooks on the same topic increase cost and reading load. One main book plus a revision-oriented book is a common approach.
Atlas and practical books
Practical and dissection-related books are used heavily. Check the condition and binding when buying second hand.
Frequently asked questions
Are second hand medical books a good idea?
Often yes for stable subjects, provided the edition is current enough for your teachers and exams.
How do I check the edition?
Look at the edition number and year on the listing, or ask the seller before ordering.