Proficiency, Spell Penetration, and Lore Items

[ivarthevic]

Edited - thanks for the comments.

Do I have any of this wrong?

What items should I equip for which spells?

Scorching Ray and Wall of Fire - Potency and fire lore item set.
Magic Missiles - Potency and kinetic item set.
Web - Conjuration item.
Phantasmal Killer - Illusion and spell penetration item set.
Hypnotism - Enchantment and spell penetration item set.
Ray of Exhaustion - Necromancy and spell penetration item set.
Cone of Cold - Potency, ice lore, and evocation items.

Understanding item effects

Potency items increase the damage of the spell. There are two types of potency items: general potency items and items that increase the damage of specific spell types (e.g., combustion items increase the damage of fire spells only).

Spell penetration (SP) items help overcome spell resistance on the basis of the formula: 1d20 + your caster level + any feat, enhancement and item modifiers => character spell resistance.

Spell difficulty class (DC) modification items help overcome the saves against the spell using the formula: [10 + Spell Level + CHA mod + feats + items] => d20 + character’s reflex, fortitude, or will resistance. As can be seen, the Heighten Spell feat increases the effectiveness of spells with a save check.

Spells that benefit from potency and lore items

Spells that have no spell resistance check (i.e., that do not benefit from a spell penetration item) and no save check (i.e., do not benefit from a DC modifier) include: fire wall, magic missile, force missiles, solid fog, acid fog, globe and lesser globe of invulnerability, acid rain, scorching and polar rays, and obscuring mist.

Spells that would benefit from potency, lore, and DC modification items

Damage spells that have no spell resistance check but do have a save check include: Cone of cold (Evocation school spell with Reflex save).

Spells that would benefit from DC modification items only

Crowd control spells that have no spell resistance check but do have a save calculation include: Web (Conjuration school spell with Reflex and Strength saves).

Spells that would benefit from spell penetration and DC modification items

Spells that have both spell resistance and save checks include: Phantasmal Killer (an Illusion school spell with a Fortitude save), Hypnotism (an Enchantment school spell with a Will save), and Ray of Exhaustion (a Necromancy school spell with fortitude save).

[sephiroth1084]

Looks like you've got this pretty well understood. If you can find a good potency item (instead of multiple element-specific items, like combustion and glaciation) you can cut down on stuff to carry. When I was leveling my wizard, I managed to find several scepters with two different school focuses on them (Necro and Illusion Focus, for example). I had a set with potency/appropriate lore for each of the 3 elements I tended to use most (fire, cold, acid), one set with a dual-focused scepter coupled with a spell pen. scepter, and another set with the remaining schools.

Later on, I found some bracers and such that had enchantment focus, so that freed up a weapon group, and then I got a necklace with Spell Pen. 6 (check the AH...cannot recall name or level right now, but probably around lvl 9-12ish). When you get into Gianthold, you'll want to run The Reaver's Fate semi-often in the hope of getting the Stormreaver's Napkin (cloak with +6 Int and Spell Focus in all schools of magic--doesn't stack with other such items), which will free up a lot of slots. Another item to aim for is the blue dragonscale robe, which has potency VII, spell pen. VII, Greater Lightning Resistance and greater arcane lore (greater lore for all arcane spells, yes, even Disintegrate).

As for proficiency...I didn't see a direct question, but did see it in the title, so I'll assume here that you were wondering whether proficiency with a weapon matters for a caster. It doesn't really unless you're intending to melee a lot. I find that the only times I melee on my wizard are when I have Held or stoned something.

[Arianrhod]

I think Cone of Cold is Evocation, not Conjuration

[Junts]

sr opposing your spell pen doesn't roll a d20: its d20 + your caster level + misc mods vs spell res figure