Number of cards: 69 (minus Fusion) (I think that this amout suits me well, because that's how many I can use effectively)

Number of currently banned cards: 2 (I take them out in tournaments)

Monsters

Winged Kuriboh lv10
Mythical Beast Cerberous
White Magician Pikeru
Old Vindictive Magician
Sorcerer of Dark Magic
KuribohMystic Lamp
Dark Magician Girl
Chaos Sorcerer
Dark Eridicator Warlock
Breaker the Magical Warrior
Apprentice Magician x2
Dark Magician x3
Ebon Magician Curran
Blast Magician
Tsukuyomi
Skilled White Magician
Rapid-Fire Magician
Buster Blader
Magician of Faith x2
Chaos Command Magician
Winged Kuriboh
Skilled Dark Magician x2
Dark Paladin

Spells (*=banned)
Monster Reborn*
Premature Burial x2
De-Fusion
Yami
Pot of Greed*
Poison of the Old Man x2
The Shallow Grave
Diffusion Wave-Motion
Gravekeeper's Servant
Dian Keto the Cure Master
Emblem of Dragon Destroyer
Nightmare's Steelcage
Spell Absorption
Nobleman of Crossout
Magical Dimension x2
Magical Blast
Transcendent Wings
Infinate Cards
United We Stand
Polymerization
Swords of Revealing Light
Dark Core
Dark Magic Attack
Mystical Space Typhoon
Heavy Storm
Mage Power
Lightning Vortex

Trap
Success Probability 0%
Magic Cylinder
Dissapear
Spell Shield Type-8
A Rival Appears!
Divine Wrath
Seven Tools of the Bandit
Cursed Seal of the Forbidden Spell
Sakuretsu Armor
Ultimate Offering
Call of the Haunted

Well, I started off with just a Spellcaster's Judgement, but then I suped it up and made it better, but it still needs work. Also, the reason I have those non-Spellcaster Monsters (Buster Blader and the Kuribos) is because despite the fact that they're not my primary card type, they still have very useful effects.

So, what do you all think?

Well, I'll try to be nice. I am only trying to help here. In general, competitive decks should be no more than 43 cards, and that is pushing it. For fun, this deck is fine. And it is unfocused. You said you wanted it based on Dark Magician.
Here is a build that might suit you a little better and make it a little more competitive.

Monsters-18

Dark Magician of Chaos
Dark Magician x 2
Skilled Dark Magician x 3
Mythical Beast Cerberus
Gravekeeper's Spy x 2
Magician of Faith
Apprentice Magician x 2
Old Vindictive Magician
Sangan
Exiled Force
Mystic Tomato x 2
Breaker the Magical Warrior

Spells- 15

Tribute Doll
Graceful Charity
Nobleman of Crossout
Magical Dimension x2
Nightmare Steel Cage x 2
Dedication through Light and Dark
Scapegoat
Swords of Revealing Light
Smashing Ground/Fissure/Hammershot x 2
Premature Burial
The Shallow Grave
Book Of Moon

Traps- 8
Mirror Force
Sakaretsu Armor
Torrential Tribute
Dust Tornado x 2
Call of the Haunted
Ring Of Destruction
Compulsory Evac Device.

That gives you a decent build for a Dark Magician deck. It also gives your deck a little speed. Hope this helps.

Well, that is something I'm shooting for, but I have no way to get the cards I need. Also, I like to keep the Dark Paladin in there, for good measure against Dragons.

Well, that is why I said that was a basis for your deck. Whatever you don't have, find something similar that can help the theme. Alot of the cards I mentioned were reprinted in either the Dark Beginnings or Dark Revelations sets. Put your own personal touch on what you want. There is also the sidedeck to consider. Sidedeck the Buster Blader so that you can use him if you need to.

Actually, I copied and pasted the Deck List that you made, and now I'm going to look for those Boosters. What Booster does Mystic Tomato come it?

Mystic Tomatoe was in Metal Raiders, Dark Beginnings, and the one of the earlier starterdecks.

OK, one more question, what about Mirror Force and Scapegoat?

I just remembered that I don't have Sangan, or Gravekeeper's Spy, either... Could you tell me where they are, if you know?

to be honest, Just get the Dark Beginnings/REvelations sets. They are reprints of all the series from Legend of Blue Eyes through Ancient Sanctuary. They have all the cards that you need. Also the newer structure decks have a lot of good cards. Otherwise the trade forum here on the realsm or e-bay may be a better way to go.

And just a friendly reminder here, try to use the edit button on your posts to continue a question instead of making a new post.