Shield of Light: In theory, the spell offers some interesting options (like the ability to conjure spiked shields, and to allow a medium arm-worn as an armor tert guild), in practice I don't use it as anything beyond a basic shield skill buff. Currently between PoM, MF, Halo, Benediction, MaPP, and MPP I don't have near the slots to spare. Maybe someone with 1600+ Arcana and 11 OM slots can weight in but this seems like a tertiary OM option to me.
Spells: If you have an interest in PvP I'd consider SL, same for FoU, though for FoU I'd note it also performs well when hunting during those gaps where high-spawn undead aren't readily available. I personally also like CHS and SA, spiritual combat is unique to Clerics and I enjoy sucking the souls from things till they die, though I should note this is 100% a meme and not as effective as just blasting them with TM.
Theurgy: Meraud and the accompanying rituals is the bog-standard way of training Theurgy and moving it to high mindstates. I would note that Tasmine/Kertigen are a relatively low-cost way of keeping Theurgy in active mindstates during extended hunting trips, so don't overlook the trickle approach.