I spent about $400 on books for this P1 year. I probably could have gotten away with $0 on books if I wanted to be really stingy or maybe $260 judging from the books I've actually used. I've used Goodman/Gilman, Lehninger's Biochemistry (somewhat), Pharmacy Drug Cards, and Foye's Medicinal Chemistry (somewhat useful for finding the prof's mistakes

) - the others are gathering dust as we speak.
At my school, at a lot of professors talk about "required" textbooks. What they mean is, "this book will go into more detail than I'll present and it might/might not be useful to you". Your school may be different in how they use textbooks.
Amazon.com is a good place for pharmacy books. You can save 40-50% off the list price and delivery is usually quite speedy.