Some people argue that on akali you should make hextech gunblade but i prefer will of the ancients cause it gives more ap. with this build at lvl 18 you have around 121% bonus m dmg(around 700 dmg/ulti hit and around 1k dmg for mark of the assasin combo. it has decent hp due to rylai no1 gets away from you due to slow from rylai mag pen is good due to boots&void staff also from runes. akali has low cd spells so you will hit like a truck. in teamfight you always go for the enemy assasins/mages(they die from 1 ulti&1 mark of the assasin). also when ever you fight use twilight shroud for the opportunity to run but also for the bonus armor.