Okay, I will bite. There are four items you can wear that will take a magicka cost reduction (five if you count the falmer helm and wear it in conjunction with a circlet). You can get a maximum of 25% reduction in two schools per enchantment (29% if you fortify enchant with alchemy). That's a maximum of 290% reduction. It takes a 500% reduction to get free casting in five schools, So, how do you get all schools free to cast?
I'll clarify since you asked. No, I was not speaking about the Fortify Restoration glitch, as you wouldn't really need to reduce the magicka of all schools when you can just have an insane amount of never ending magicka supply all in a single enchantment effect. If you haven't already realized it, I don't much care for the Fortify Restoration glitch. You might as well do tgm and call it a day.
Anyhow, moving on. I stated that you can technically get 100 percent reduction in all schools simply because you can. Even without the Fortify Restoration glitch. How you ask? Simple. You obtain the Steed guardian stone power. Makes what you wear weightless. Now you just do the mathematics (It's been a while, so bear with me), and make a set of armor/jewelry for each combination. If I recall correctly, it was around 7 sets.
Whatever type of item that you're wearing is weightless, including items that are not currently equipped. So 7 sets of Daedric cuirass'? All weightless. So theoretically, you can easily have all schools of magic cost 0 magic since you have sets of equipment for each possible combination of magic schools (Only two available at any one time with your left and right hand). I imagine on the console it would be a pain to be switching items about, but on the PC the customized favorites menu makes it a bit easier.
You can also just skip the middle man and console yourself the reduction since you technically have it and it wouldn't really be cheating, just cutting out the inconvenience of switching gear. Granted that means that you always have to be in armor because if you unequip it, you'll probably be overencumbered if it's something like Daedric armor that you did this procedure with. Just my two cents.