for a keep the powers low you can also go with-
15 Multipower, 60-point reserve, (60 Active Points); all slots Requires A Roll (Skill roll, -1 per 5 Active Points modifier; Must be made each Phase/use; Magic skill; -1 1/2), Side Effects (-1), Gestures (-1/4), Incantations (-1/4)
1 fire ball: Blast 8d6, Area Of Effect (8m Radius; +1/2) (60 Active Points); Requires A Roll (Skill roll, -1 per 5 Active Points modifier; Must be made each Phase/use; Magic skill; -1 1/2), Side Effects (-1), Gestures (-1/4), Incantations (-1/4)
deadly for the user, that is -12 to the roll