A lot of herbs are common, garden-variety, cooking ones, so either get them fresh at grocery stores or plant a little garden. A lot of magick doesn't need any extras, as really, it's all about intention and force of will.
As far as a Book of Shadows goes, what that really is supposed to be is a blank book in which you write down all that you learn and about your magickal workings. If you can look online, some witches have posted bits of their learnings and teachings as online BOS. Traditionally, if you join a group or coven, you hand copy from the group book to start your own.
An athame is a ritual knife. That means it was never and will never be used for anything but ritual. After that, which type of knife you choose is up to you. Some folks get really specific about types of metal, decorations, etc but remember this is a symbolic tool so it probably could be just about any knife.
- Rae