1. 70
That equals +500% spell damage.
As for the wanderers scrolls, here goes:
Titan Sword, Titan Armor, Fortune Smile - keep those for the fights with bosses, heroes and castle sieges.
Ancient Knowledge - use this against heroes level 40+ and bosses. Since it's enough for 5 combats, leave the heroes alive and then simply slap on the scroll and mop them up after you cleaned up the area.
Flaming eyes - keep this for bosses only. +20% leadership against bosses helps immensely.
Depth of though, mad rage, magical flow and such - use those against bosses and when you feel your max rage or mana may not cut it.
Song of the Wind, Call Death, Call Collosus - those are best used when you have the need for extra troops. Call Collosus scroll is extremely useful early i the game, as it will spawn a lvl 5 unit which alone may beat up the enemy troops even on impossible. All it needs is some help from spells.