That's a tricky question, we recently had the discussion about hedge magic. Philipus Niger in GotF is designed without obeying what core rules say about this!
But to compare with Hermetic magic then you need separate spells for each of the Forms.
So unless dispelling powers of demons (or faeries for that matter) I'd say you need one for each Infernal [Form equivalent] Power, so 10 in all. Just like Hermetic Magic.
And for Gruagachan you'd need one for each hedge art: Curse, Blessing, Shape, Vision...