Amethyst Crystal (525g)
Stats: 5% CDR

Rigor
Recipe: Amethyst Crystal (525g) + 625g = 1150g (or make it double Amethyst Crystal)
Stats: 12% CDR, 7% Movement Speed and [+10 Magic Penetration OR +10% Spell vamp]

Night's Fury
Recipe: Rigor (1150g) + Rigor (1150g) + 575g = 2875g
Stats: 25% CDR, 15% Movement Speed and [+25 Magic Penetration OR +25% Spell vamp]

These items kill three birds with one stone.
# Movement speed for casters (although I respect they possibly don't deserve any),
# If spell vamp, an item AD Casters can buy without wasted stats
# CDR without mana/mana regen (on a caster item), which players have been asking for.

They consume a slot without providing any damage, which I feel is a suitable balance... or at least a fair trade. I also think the lack of damage at all stages justifies nothing being unique, but any amount of the stats could be made unique.

Due to casters lacking attack speed and critical strike, I had to create a "basic item" that would build into these. Feel free to propose alternates. The Amethyst Crystal could be used in the recipe for other items such as Brutalizer (Long Sword + Amethyst Crystal, for example). Or it could not be intergrated into existing items at all.

Spell vamp or magic pen? Magic doesn't have a equivalent to critical strikes.

For a second I'm sitting here like "now wait, an early game item for a stat that maxes out at 8x it's starting value? And then I remembered; CDR is always a Unique passive, so two of the same CDR item isn't useful anyway. Make the builds, instead of self-stacking, into different items. Make one suggestion build into Haunting Guise, another into Hextech Revolver, maybe have it build with Ruby Crystal into Kindlegem...oh and lower the base cost if you're going to do that last one.

Cooldown reduction is only unique at the moment because all items list it as unique. Stacking Amethyst Crystals would work, but it doesn't provide any real stats of its own. Also, if Rigor was unique then requiring two of them would be redundant.

Both Hextech Revolver and Haunting Guise provide AP, which I didn't want these items to contain... otherwise AD casters can't use them. But Kindlegem is a possibility. But I was going for a glass-cannon item (like Zeal and Phantom Dancer), whilst health provides sustain.

I wouldn't mind creating other items that use these items though.

The only problem with CDR is it scales very differently on different champs skills. You've got anything between the (I think) 0.5 second CD on placing Teemo's shrooms to the 180 second CD on Karthus' ultimate. That and the fact that it's just 50 gold more than you start with is like taunting people "haha, you can't get this early game, :P" make it worth more, something like 650-800 ish. That and also if CDR was in an early game item like that, it would probably change up certain item recipes. Dunno how it would work out.

To be fair, CDR is the same for every champion. A percentage is a percentage. People with large cooldowns are getting more knocked off, so they will notice the difference more.

As for its price... making it affordable from the spawn is pointless, because it provides nothing for the first few levels. Yes, maybe it'll let you harass more often... but it has no damage, no sustain. There's no health, no mana, no regen, etc. It'll be purchasable from the start in Dominion.

You're right, it's hard to see if it'd work from just words.

Well regarding the AD caster item, Don't we already have a brutalisers?