The best way to play Auto Cast SC is to optimize MATK and get some Autocast. Most Gear/Cards looks nice but are not worth it in a Long turn. I play ASS Chaser by myself (because its fun) and I can give you some suggestions of what you can do and build to make it somehow strong, but always remember its an Fun Build. Headgear:
For Headgear I can only tell 2 Options, Smokie Trans. Leaf and the Inconspicuous Hat.
Smokie gives alot of new and strong Autocasts (Chain Lightning is 1% chance if I remember correct) and the Inconspicuous Hat gives massive Matk. The Question is what you need more. If you choose Smokie, you neet atleast +10 it (Can be simple because of Weekly Quests) and the Inconsp need atleast +7-9 to be effective. If you choose Smokie, be sure to get Matk from other sorces.
Wickebine's Black Cat Ears will be a great choice if you dont take Matk Pierce from Shadow Gear/Card Combos. Weapon:
Next Chapter for important decisions is the Weapon. Most people pref. Faceworm Queen leg because of the strong EQ Autocast (which scales still with Matk here). The other Options (and more expansive) are the Illusion Bazerald which Boost Matk by a good amount and boost some Fire Skills or Platinum Dagger which is the strongest Dagger (but extrem expansive because of the Memory Enchant).
The other Weapons sounds nice but hard to execute and in the end not worth it. Maybe Old Parasol can be considered but im a not a fan ot this.
As for the Madogum, I dont have any clue how good that is actually. Never saw it in Action but maybe its worth an try.
You can still get the Immortal Wind Ghost Card for the juicy Killing Cloud Level 5 Autocast, which is kinda underrated. Accesory:
Last but not least this. Alchemy Glove will be the cheapes Option because of Autocasts and Dmg increase for Fire Spells. But in the end you will need Life Leech and Power, so getting the Illusion Booster (Matk one) with the Hp Reg Enchant, Spell, Aspd and the King Schmidt Accesory for the Temporal Combo will be must have in most ASS Builds.
For Cards you can still increase Dmg depends on your Main Dmg sorce (Mavka for more Fire and Elvira for more Wind) or go for the strange Card Combo from Owl Visquant and Marques (How are they spelled the Nightmare Clock Owls?).
Rest of the gear is focused on Matk, Aspd, reduce and other magical dmg boosts.
As for Mvp Cards:
Lich Lord: Would be insane good
Dark Lord: Still a good option
EL-A17T: Not good, dont do it
Baphomet: Aoe Attack can trigger autocast which can be insane in Mobs.
I dont know if that help you, but this is my thought of this. Most iteams sounds good but are still traps sadly...