Versus a melee match up, be sure to perma use your "q" on your enemie, it allowes you to put free harrass and psychological advantage. Get ready to dodge all skill shots with your amazing movement speed masteries and hve a free sustain with your glorious passiv !
To my opinion you should have everytime a ward in your pocket to allow you to see the ganks incoming. Personnaly I have the free ward + one on me 24/7, it allows you at level 6 to do crazy escape jumping on wraiths !

When you took too much damages from your match up, don't hesitate to build the T2 of Zohnya or a Negatron, it will be usefull anyway, and you will have insane damages no matter what cause ... YOU ARE A NINJA! Don't loose hope, farm and wait for the time fo PENTA!

Akali has allmost her Gunblade, it's time to kill ! Don't hesitate to roam on botlane, 2 free kills are waiting you ! Even with a good vision inthe enemy jungle you can cucucuucucucucucucucucuonter jungle like a boss ! Never forget to have a ward to free escape on the jungle creeps !

With presaison, oracle has disapear, only pink wards are your nightmare, DON'T JUMP IN if they put one, just help your adc to kill the tank, this way you will have a free dash and dodge all cc ! then just face roll / penta.
Their is 2 ways of playing akali in team fight : in front of the fight or behind, go behind their team only if you are sure about escaping and killing the adc.
In solo Q people do a lot of mistakes, no matter your elo, just keep your mind cold farm and jump on a guy ONLY if you are sure to kill him.
Good Luck Summoner and KILL THEM ALL!