Autocasts should be based off another autocast spell, except arrow spells. They cannot be detected through "Unit Starts the effect of an ability". They are far too tricky to be obtained through basic triggers and make them MUI as well.
Auras, indeed depend on its effect. If they are supposed to give certain bonuses to units affected by aura, then we have a problem. If you just want them to do an effect around the caster to all the allied/enemy units, like healing them every second, or stuff like that, then its very easy. Just pick up every unit with the aura ability, followed with the pick up of every unit around the unit with the aura, and do the effect. Make this a repeating trigger.
not icons. I just want to know how to make them autocast or an aura.
So basically, to make a healing aura, you make a trigger that says, Event: unit is under the effect of spell or something like that. Condition: ability in effect is equal to 'Healing Aura' Action: modify effected units health?
Event - Every 1.00 seconds Actions - Pick Up Every Unit in the playable map matching condition Level of Ability for (Picked Unit) greater than 0 and do actions -> set cast = picked unit -> Pick Up Every Unit within x range of cast and do actions -> Set life of (Picked Unit) to Life of Picked Unit+y - set cast = null
(aura)you could use a dummy unit which follows the hero arround, casting the spells effect which you want on any unit which comes in a specific range of the hero, and continuesly do this when the effect runs out.
But this is just a rough idea maybe someone else can refine this idea for u.
This is dumb and I don't suggest it. How can a single unit keep casting Faerie Fire around for example? Every unit has a little cooldown period (even without cooldown) between spells. And keeping a dummy unit follow the hero around... nope! I definitely don't suggest this!