Most important mercenary/warrior helmets that give +% speed to the troops training in barracks, crucial for making WW hammers, and off players who want/need to make most troops in main - hammer village.
but also Lance of Phalanx for def if Gaul, Morning Star if you are Teuton (always very expensive +5) and Boots of Enlightenment. Maps and Horn of nataras are also important. And in start the regeneration armors so you can go for more adventuresses.