Paizo BLASTER CASTER build:
Goal: Pile on the hurty-hurt with direct
damage spells. You don't need battlefield control if the enemy is
dead.
Level 1: Take Sorceror: Crossblooded Orc/Draconic, Human, take
Varisian Tattoo, take Trait: magical Lineage (pick spell), Reactionary
(+2 Init)
Then take Wizard/Evoker -Admixture Specialist for your remaining
levels. Why Admixture? Because you can change the element of any of
your blasting spells on the fly to get around elemental
resistances/immunities.
If you want to superspecialize outside of Evoker, take Sin Magic, lose
two schools (Conjuration/Abjuration), gain yet another spell slot per
level of raw power.
Key Feats: Intensify Spell, Empower Spell, Quicken Spell, Spell
Perfection, Spell Penetration, Spell Specialization, Greater Spell
Specialization.
End result: Crossblooded sorc orc/dragon bloodline 1, Wiz/19,
Admixture Evocation specialist. Note: Can use Sin Magic for more
slots. Sorcerer level allows use of spell devices from denied schools
(Conj/Abjuration). Magical Lineage Trait allows Intensify for free on
chosen spell. Spell Perfection allows free Quicken at higher levels.
Play Hints:
Take Burning Hands or Magic Missile as a Specialized Spell early.
Burning Hands will deal more damage, Magic Missile has better
long-term utility and keeps you out of danger. Every other level, you
can change your specialized spell.
Add Greater Spell Specialization at level 7 or 9. Why? You can then
memorize utility spells, and trash them for your blaster spell.
Change your specialized spell up to Scorching Ray or Fireball when you
can, depending on campaign, typically at 5 or 7.
At level 12 or higher, change it to Fire Snake. Use Admixture
specializing to change the element on the fly.
Use Fire Snake until higher levels. Why? High damage base and level 5
spell still leaves room for metamagic, esp Quicken.
Mechanics behind Choices: Orc blooded, Draconic: +1 to all damage
spells, +1 to element of choice, retasked by Admixture = +2 dmg/die on
blasting spells.
Feats
Intensify Spell: Increases caster level damage cap +5 to apply
to a specific spell. Burning hands goes up to 10d4+20. Magic Missile
goes to 7d4+14. Fireball to 15d6+30, Fire Snake to 20d6+40.
Empower Spell: Increase dmg by 50%.
Quicken Spell: Hit enemy with two spells/rd.
Spell Specialization: +2 to caster level with a specific spell. Helps
bring the damage earlier and faster.
Varisian Tattoo: +1 to Caster level with a specific school (Evo). This
buys off your sorc level.
Greater Spell Specialization: Sacrifice spells to power your chosen
blaster spell. Means you can memorize utility spells freely.
Spell Perfection: Doubles fixed feat bonuses, apply one metamagic for
free. An Empowered/Intensified spell with Magical Lineage is still its
original spell slot. SPell Penetration doubles to +4. Varisian Tattoo
to +2. Spell Specialization to +4. Effectively, you've got +10 on
Spell Resistance rolls, and are casting 'Your spell' at 5 levels
higher then your own.
Top End Damage: 30d6 +60 from Fire Snake, empowered, Intensified,
average 165 dmg, save 1/2, level 5 slot. Quicken for another hit, 5th
level slot, 20d6 + 40dmg, avg 165.
= 330 blasting dmg in one round, save for 1/2. If you've a Rod of Maximize, you can lift this to 215 base damage.
Base level 5 spell slot is 20d6+40 dmg, 165 dmg.
By Level
At level 1, your Burning Hands should be 2d4+4 (avg 9)
At level 2, its unchanged.
At level 3, Spell Specialization kicks in. 5d4+10 (22.5). This tops it
unless you Intensify it.
At 4th, 6d4+12 (27), Intensified BH.
At 5th, Intensified BH, 7d4+14 (31.5).
At 6th, you can shift Spec to Scorching Ray. 2x 4d6+8 (44). Your
Fireball is 5d6+10 as well, or 7d6+14 if specced.
At 7th, 6d6+12 fireball, or 8d6+18 if spec. An Empowered, Intensified
Burning Hands, if still the spec spell, is 13.5d4+27 (about 60).
8th - Empowered Scorching Ray, 2 x 6d6+12. E/I BH is 15d6+30 (74, max)
9th - Intensified, Specialized Fireball is 11d6+22 (51).
10th - Firesnake. E/Spec Fireball is 15d6+30 (74). Emp Scorching Rays
are 3 x 6d6+12, or 18d6+36 (99 dmg). You can now Quicken a Burning
Hands or Magic Missile as kicker damage in a round, although you've
few slots.
12th - E/I/Spec Fireball is 21d6+42 (115) damage. You can now Quicken
a 12d6+24 Scorching Ray.
14th level - A Specialized Firesnake now exceeds/equals an intensified
Fireball. Fireball caps at 22.5d6+ 45 (123~) damage. An Empowered
Firesnake is 24d6+48 (132) damage. You can now Quicken a 10d6+20
Fireball. Intensified, Empowered Scorching Ray tops out at 24d6+48
(132 dmg)
15th level - Spell Perfection. You can now add a Meta for Free. This
will be Quicken or Empower. Intensified might be free if Magical
Lineage applies to it. Caster level buffs for spec spell exceed +5, so
top out at 20d6 dmg at 15th level. You will miss Spell Resistance
rolls against CR appropriate enemies on a 1. Assuming Firesnake, you
can now cast a Quickened Intensified Firesnake for 20d6+40 (110)
damage out of a 5th level slot, and an Empowered Firesnake out of the
same slot for 30d6+60 (165) damage. Using a 7th level slot, you can
Empower both.
16th+ - Damage remains the same, higher level spell slots are open for
use of other Metas or control spells.
Conceivably you could use Disintegrate to get a higher damage total,
but the delay isn't worth it, and you'd lose the Varisian tattoo
bonus.
If your DM allows you Twin Spell from 3.5, you can very, very easily
clock in at 495 raw dmg/round. IF he allows Arcane Thesis, god help
your enemies.
Best Answer
The basis for optimized blasting in 3.5 is the mailman. Specifically, the goal is to have an extremely reliable nuke, that happens to deal enough damage to kill anything. Ultimately, maximizing damage isn’t the hard part, it’s making sure nothing is immune to that damage.
Force damage is usually a good starting point, since force is very rarely resisted. For these purposes, wings of flurry and manyjaws seem to come up a lot in conversation; wings of flurry, in particular, is a devastating sorcerer-only spell that deals d6/level force damage with no maximum.
For things that are force-immune, going with fire or cold, and then habitually using Searing Spell or Piercing Cold, works wonders. While fire and cold resistance/immunity are the most common energy defenses out there, with Searing Spell or Piercing Cold, at least 50% of your damage is going through, yes, even then. As far as I know, nothing in the game is immune to the special super-fire/super-cold damage that these metamagic feats give your spells.
And of course, you want ranged touch attack spells that don’t offer saving throws and are SR: No. This is getting you pretty close to a 95% chance of killing any opponent as a standard action.
The key thing to realize here is that we are talking about one or two very carefully chosen blasting spells. This “blaster” really doesn’t know many blasts. No wasting time with different energy flavors, because the force and super-fire/super-cold damage we’re working with is nigh unresistable. No grabbing different AoEs, because AoE spells allow Reflex saves and usually allow SR, and those are too unreliable; we’re going for the reliable single-target kill.
And that leaves all of our other spells for, ya know, everything else. Utility, you’ll have in spades.