Love the champion. When I first started playing the game, I browsed the champions back then and I saw Akali. Good memories. I haven't played Akali much recently, but I still have the champion, and she is still my favorite champion.

Although I haven't played her recently, I still believe that she's a strong solo top or middle to counter certain champions. She does an incredible amount of damage early game, and the moment she hits level 6, she terrorizes people with Shadow Dance because she can jump to the champions to nuke them.

Greater Mark of Attack Damage
Just a small amount of extra Attack Damage is helpful in getting her passive rolling early game.

Greater Mark of Magic Penetration
Delicious burst damage.

Greater Seal of Vitality
The health is helpful against ganks and 1v1's with strong, healthy champions. Keeping you healthy also intimidates quite a few other champions that also nuke but have very little health.

Greater Glyph of Scaling Ability Power
I enjoy the scaling Ability Power glyphs to make her stronger, especially by the levels at and after level 6.

Greater Quintessence of Ability Power
Makes her single target nuke like crazy early game anyways.
Makes her hurt some more.

Get the extra Attack Damage & Ability Power, Summoner's Wrath for Ignite, and that extra health. Going down the left tree makes her incredibly powerful, as her damage is scaled percentage wise, especially when they're close to half health, making it easy to proc Executioner .

Boots and Health Potions are used in many of my solo top champions. This allows Akali to move around easier to get last hits and harass with Mark of the Assassin. Health Potions are for exchanges and survivability in case of unfortunate scenarios.

Hextech Revolver is naturally for Akali. It helps her sustain herself, and the ability power is nothing to laugh at as it makes her that much more bursty. Builds into Hextech Gunblade.

Mercury's Treads is a natural choice to keep yourself protected.

Rabadon's Deathcap makes her incredibly powerful and will most likely allow her to quickly burst down any champion.

Giant's Belt is to keep her alive in case of focus and Oracle's Elixir. Builds into Rylai's Crystal Scepter.

Hextech Gunblade is built from Hextech Revolver. It gives her a target slow and gives Akali a great amount of Attack Damage and Ability Power. You can also choose Will of the Ancients instead of this item.

Rylai's Crystal Scepter builds off of Giant's Belt. Makes her Shadow Dance instantly slow your opponent and keeps them locked in a slow. It gives her a good amount of Ability Power and health for survivability. This can be swapped out for any other survivability item, like Zhonya's Hourglass.

Lich Bane makes her attacks in between abilities blow up the enemy. Too good. Get it after you get a decent amount of Ability Power; do not rush this item.

Guardian Angel for resistance, armor, and overall survivability to keep you in the fight.

Shadow Dance maxed whenever possible. For some reason many people don't know this, but Mark of the Assassin is where most of the damage comes from. Shadow Dance just keeps Akali up with the enemy, so Mark of the Assassin should be maxed as soon as possible to keep that explosive damage. Crescent Slash should be maxed second, as it clears minions and is sometimes helpful in team fights. Akali is a single target nuke, but Crescent Slash makes it so she can perhaps intimidate squishy champions near her target. Twilight Shroud is incredibly helpful, and it is what makes people buy Oracle's Elixir, but you won't need it as much as the other skills considering you need to make sure you take them down. This skill should be used wisely as the cooldown for it is fairly long.

Ignite
Perfect for single target nuke. This keeps the person from healing, life stealing, spell vamping, and many other things. It also catches them in case they get away from you, which is difficult to do, so it gives you the kill in order for you to scale faster. Great skill overall.

Flash
This is used for escape solely. There are very few occasions in which you'll need this to chase anyone. Shadow Dance makes it so it will be very easy to chase enemies, so Flash combined with Twilight Shroud makes it difficult for enemies to catch on to where you retreated to.

Gotta' love Akali. She's very strong, but she can be countered fairly easily as well, so play smart and carefully with her.