The artifact mage pseudo-cycle (Trinket Mage, Trophy Mage, etc.) are all exceptional choices
What's strange is how much of the core Madrigal synergy is missing from it
Narset, Parter of Veils I was extremely dismissive of this card when I was doing my first past through on War of the Spark
At the time of writing, TCGPlayer is also listing this card with an estimated $1,500 price tag, though that number is going to be fluctuating once more copies of this Disney Lorcana card start showing up for sale
Otherworldly Gaze If you count Surveil spells as self-mill (and I do, given how rarely you see triggers that care exactly how cards end up getting from your library to the graveyard), then Otherworldly Gaze is as good a choice as any for the most consistent, efficient, no-bells-and-whistles version of the effect
The regeneration ability is especially helpful when its protecting those value-engine creatures