Vortex fits with everything, really.
Fireball and Blades give the most damage.
Snow Storm is also a very good spell to combine with Vortex: the combination makes the spell duration four times longer and is very effective for both targeted and area casting.
The best combinations for me are: Vortex + Snow Storm (Damage + Stun +
Very Long Duration/ Large Area + Targeted = 4x Area)
Vortex + Blades (Damage + Stun + Long Duration/ Area =
4x Targeted)
Fireball + Blades (Massive Damage/Targeted)
Fireball + Force Push (Large Damage/Targeted + Area) Never combine Snow Storm with Shock, Fireball or Force Push though; these combinations suck.
gaming.stackexchange.com/users/4592/DennisMock
Fireball + Shock is what I always used.
It looks neat and it pretty much destroys anything when fully charged.
Use it when you are surrounded by a lot of enemies.
Not only does it cause considerable damage, but also stuns them for 4 seconds or so, allowing you the time to safely charge up another finishing blow.
gaming.stackexchange.com/users/None/
I think you want spells that both stun and hurt the enemies, so: Fire, Shock, Blades and Storm do damage Vortex, Force Push and Shock (again) seem to stun or push back
I'm not sure, but
from experience, one from each category works the best, and after that it's just personal preference.
gaming.stackexchange.com/users/4012/Ronan
Vortex + Blades got me through a large portion of the game.
Vortex throws the enemies around, while the blades auto-hit for a good amount of damage.
It isn't as impressive when throwing the spells in a particular direction, but it really shines when doing the area attack.
gaming.stackexchange.com/users/3015/Rapida
I found Shock + Vortex and Fire + Blades to be the 2 greatest combinations.
Personally, I use one that "fits me", which is Vortex + Snow, though I don't know if you would like it, so I won't say it's the "best".
Either way there is no such thing as the "best" combination of spells.
It depends on what you like most.
Damage?
Fire + Blade.
Duration?
Vortex + Snow.
Both?
Vortex + Shock.
Try them all and see which one fits you best.
gaming.stackexchange.com/users/None/
Is there a significant difference between different combinations of spells in Fable 3? I've found Shock + Vortex to be satisfyingly destructive. But are there better combinations? Do some combinations get bonuses, or is it a matter of taste?
What combinations of spells are the most effective?
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<fable-3>
gaming.stackexchange.com/questions/10206
gaming.stackexchange.com/users/847/Seamus
Fireball and Blades or Fireball and Shock give the most damage.  A combination of the following is the best you can do, fireball, blades, shock, vortext and fire. 
A variety of combinations are suggested. 