This build is mainly for people who want to get an edge playing Akali, and may be similar to some builds, but vastly different from others, due to the fact I omit one item that most Akali builds include.Hextech Gunblade, disgusting.

Akali needs to rush her Rylai's in order to have maximum damage output, simply because the spamming of skills you do as Akali will permanently slow your enemy, making it easier for you to pick off the right target in ganks and team fights.

For Akali, I run a pretty simple rune book:

9x Greater Mark of Insight ( Magic pen )
9x Greater Seal of Evasion ( Dodge )
9x Greater Glyph of Force (AP / level )
3x Greater Quintessence of Potency ( FLAT AP )

The reason I run these runes is because:
Magic pen is essential on all chars who deal an immense amount of magic damage.

Dodge is always nice to have because 1) I run 9/21 so it stacks with my dodge masteries, and in lane you harass A LOT, so being able to dodge minion hits is vital in lane phase, and a heightened dodge chance can make it easier for you to luck out if running from an AD carry.

AP per level makes it so that while stacked with your AP quints, you get your 20 AP passive at level 2, and can start dishing out damage, as well as scaling well into late game, having roughly 48 AP from purely runes.

Many Akali players nab a Sheen and Revolver before going for their Rylais, which I find replusing. You're spending 2460 gold before you even have the best item for your character, if you saved that money and put in about 900 extra, you have the best core item on akali. Whenever people ask me why I don't get a revolver, I always say "If I did, I'd get my Rylai's 1200 gold too late.

As Akali, you always want a solo, either top (if you have a jungle) or mid, because once Akali hits 6, she is a gank machine and an unstoppable force. The tactics for both are similar, but always be careful of ganks from the jungle, so make sure you always have flash and your W to crutch out if you do not have boots.

Last hitting: If you are unable to last hit with your auto attack, try to use your Q, you have energy and it doesn't affect your staying power.

Harass: Try to Q your enemy as often as possible, and if you can get close enough with your shroud, auto attack them for the extra burst.
PROTIP: If you use your Q, wait 4 seconds THEN hit the enemy, Q them immediately after it cools down and hit them again; BOOM half of their health GONE.

Level 6: Once you hit level 6, you will want to help gank the other lanes as often as possible without jeopardizing your own towers health. Try to get some kills off of your lane rival if you can, this is the quickest way to farm your items.

Try to Always:

Before 6:
W -> Q -> Auto Attack -> E -> Q -> auto attack -> repeat

After 6:
Q -> R -> Auto attack -> W for slow - > Q auto attack -> E -> R to catch up
try to conserve at least one stack on your ult if they flash away and your flash is down.