What to buy? Beguiler/Cloistered Cleric/Mystic Theurge

[Zovc]

I'm a Begulier 2/Cloistered Cleric 1/Mystic Theurge 2 with 20,000 gold to spend. What items should I buy?

I'm encouraged to take things only from the following books:
Core (PHB 1,2 ,DMG,MM 1-5)
Complete series
Races of series
Book of Exalted Deeds (Vow of Poverty banned.)
Spell Compendium

[HunterOfJello]

What race are you and what feats do you have?
What type of character are you seeking to play? (party role & roleplaying-wise)

[Zovc]

What race are you and what feats do you have?
What type of character are you seeking to play? (party role & roleplaying-wise)

I'm an Illumian with Able Learner and Heighten Spell.

I'd like to play a character who is primarily a spellcaster in combat, but tries to be a capable party face and rogue-ish character outside of combat. He generally thinks he is smarter than everyone else and needs to do everything himself.

[Biffoniacus_Furiou]

What are your domains? What race are you using, what feats, your alignment, etc.? What books do you have available for your spell selection?

+1 Mithral Buckler, 2,165 gp
No penalties for nonproficiency, no arcane spell failure.

Spellbook, wizard’s (blank), 15 gp
Spelltrapped (CA p141), automatic reset, caster level 2nd:
Cure Light Wounds, 2,000 gp
Lesser Restoration (Paladin list 1st), 2,000 gp
This provides your party with unlimited healing, ability score fixing, fatigue fixing, etc. between encounters.

More spelltrapped books for whatever buffs you want (Luminous Armor, Ebon Eyes, Bull's Strength, Shield of Faith, Barkskin, etc.), just have the whole party refresh them between encounters.

[Zovc]

I'm an Illumian, my Domains are Dream and Fate (and Knowledge). My alignment is Lawful Neutral. I have any Wizards book at my disposal, but from the list in my OP can be used without confirmation.

The character concept I had is that I'm my Illumian's cabal is dedicated to bookkeeping, ancient knowledge, philosophy, and riddles. Their 'modern' efforts outside of scholarly pursuits are mostly related to intrigue and espionage. My Illumian's mostly interested in learning more about ancients and riddles, but has been pushed out of the cabal into an embassy where he will be ordered to tag along with his party. Oowalt is considered an exemplary Illumian by his cabal, and has been trained as an agent. He puts his cabal's orders above his personal desires, and so he's stuck with the players until his cabal is satisfied.

So, rogue-y and social gear is welcome in addition to functional Beguiler, Cloistered Cleric, and Mystic Theurge gear.

[Gurgeh]

May I ask how you qualified for Mystic Theurge at Beguiler 2/Cloistered Cleric 1? I don't see second-level spells in either class's progression so early.

[Roguenewb]

Looks like Illumian Heighten cheese.

[Gurgeh]

Ah, I see. A pretty self-serving interpretation of the rules, but I'm not the DM, so no skin off my nose.

[Chronos]

I can't remember if Runestaves are in one of the Complete books, but they're great for a beguiler, since they effectively expand your spell list. Eternal wands can come in handy, too (my favorites are Explosive Runes and Extended Rope Trick).

[Biffoniacus_Furiou]

Runestaves are in MIC, but indeed UMDing one can greatly increase your spell selection. Eternal Wands are also in MIC, and note that anyone capable of casting arcane spells can use one regardless of what spell it contains.

Naenhoon Heighten is no more cheesy than Improved Sigil: Krau or Earth Spell or Versatile Spellcaster or Sanctum Spell, etc. It all depends on the optimization level of your group, rather than what someone on the internet would consider acceptable. I'd personally prefer Krau due to fixing your caster levels, but Naenhoon: Persistent with Blur/Displacement, Glibness, Greater Invisibility, Greater Mirror Image, Foresight, etc. is extremely useful.

Spelltraps on a spellbook are specifically allowed according to Complete Arcane, traps in general and the formula for making automatic-reset spell traps can be found in the DMG. The point of putting them on a spellbook is so they'll be mobile, it's better than trapping a door and carrying it around with you.

For non-cheesy items, the +1 Mithral Buckler stands, and get some Lesser Metamagic Rods of Extend to use with buffs (Luminous Armor, Magic Vestment) and possibly offensive spells (Glitterdust, Ice Slick). Get a standard Strand of Prayer Beads which has had the Bead of Smiting removed, as per the DMG it should cost 9,000 gp (primary source). I'll always recommend a Necklace of Adaptation when it's affordable. Then there's this list (http://www.giantitp.com/forums/showthread.php?t=187851)...

[avr]

Hat of disguise, 1800 GP. I know you can cast disguise self yourself, but there's no per-day limit so if you need to be disguised for any length of time it's the better choice. Also saves on spell slots. An oldie but a goodie.

Scrolls and wands are probably underpriced relative to permanent items. A wand of web with 50 charges initially, used an average of 1.5 times per combat lasts 33 combats, which is probably past the time when you'd stop using it anyway. This sort of thing helps avoid the 15-minute workday too.