Exhaust and flash are actually a perfectly reasonable choices for her summoners. Exhaust compliments the fact that you're focusing down one target and need them to be slowed. It's a great early CC until you grab your vital rylais, which is often after you finish boots and sheen. Flash is just good on any champ, and Akali can use it for some silly juking with brushes, shroud, and walls. Other solid choices are ghost and ignite.
Amp tome is a decent starting item as well; you'll just need to play a little more conservatively without the extra 2 pots boots allows.
A great trick is the double mark that many people use. Toss a Q and optionally drop a shroud. Wait for an opening on your opponent, preferably close to the CD of your Q again (somewhat difficult at level 1 Q since it has the same CD as the duration) and then proc the mark with an auto attack, Q again, and immediately mark. Insane early game burst damage that can really scare some people.
exhausts.. good maybe early game but with rylias crystal thing that would help a lot