Cannot help here. But I'm pretty sure in the campaign I've got going on iOS, it prompted me there to buy a spell book and I did. Anyway, just so you know, if the iOS version is the same, you really don't need any spells for the tutorial. I didn't. It's light on for battles. To complete it you have to dig and find the Grail which is frustrating, and it's not even a spoiler but relief for some I'm sure if I said the Grail is somewhere in the vicinity of your first castle. Anyway, spells aren't really required in the tutorial, at least the one I did, and who knows, maybe the tutorial has some things disabled.