[K]

Its a good guide. I'm short on time so here are some abbreviated suggestions:

A few missing summons
-Ethergate gets you powerful Astral/Death Mages for boosting.
-Tartarian Gate: the Tartarians come in a variety of types, one of which gets Fire(as far as I know, the only way to "break into" Fire if you have none and don't want to Empower)
-Demon Lords: costs and requires only Blood and they get can open up almost any Path except Astral and Water depending on the one you get
-Heliopaghus costs and requires only Blood and most of them have Death
-Summon Archdevil and Bind Ice Devil has one Astral guy each
-Bind Icedevil can get you a bunch of Water mages.
-Randoms on Spectres and Hidden in Snow guys can get you into a variety of paths (you do mention Spectres though in Death).
-Wish: can get you into anything

A few missing items:

-Staff of the Elements,+1 Elemental, both the Earth/Air and Fire/Water

-Robe of the Archmagi/Ring of Sorcery/Wizardy +1 All or +1 Sorcery, are only briefly mentioned but are very useful for boosting and need their own section maybe