For my first year of law I had one textbook per module and usually a statutes book too. During the revision period I also purchased revision guides for each module. However, I only finished first year with a 2:2, which wasn't really good enough. So for my second year I'm buying all of the recommended books as it'll be easier that way with note writing. I also live about an hour away from campus, so it makes sense. If you live on campus you won't need to buy so many textbooks as some are only used for a handful of chapters which you should be able to use in your uni library or photocopy relevant info from there.
Hope that helps.