Ignite + Flash for most DPS (damage per second) and since Akali is a master assassin, this compliments her.
Akali has been recently changed so that her passive procs without any requirements. This only made her stronger and more affordable to play for players that can't accommodate specific runes for her. This setup is widely seen in other AP champs. Magic pen for assassinating low MR heroes, AP quints for more damage, and resists to beef her up.