Hi, I'm Dyzal! :3
I'm new to Mobafire and these are my first guides so please help me whenever you can to improve them and in turn improve myself! I have only just started to play ranked and as soon as the new season starts, i hope to climb high! Any comments and all that will be gratefully appreciated!

So why Summon Aery?

Summon Aery - Sure it does a little less damage then Arcane Comet but the cooldown is so quick, you will be able to cast Aery so much it could almost be considered animal cruelty! Ahri benefits much more from the sorcery line and this keystone can't be dodged.

Arcane Comet - Does a little less damage then electrocute but has a much greater cool down, which extra attacks to the enemy can make it even quicker. She also only has to land 1 hit to use it instead of 3.

Phase Rush - Ahri already has a great deal of ways to gain speed to run or chase after her enemies (orb of deception/spirit rush)

Electrocute - Is another good option for Ahri as it deals extra damage and 3 hits can be easy to land, however I chose not to use this one due to its long cool down and that Ahri can benefit much more from what the Sorcery line has to offer.

Predator - To safely channel for some movement speed and a burst of damage seems like a waste of time when Ahri already has attacks that can help her close the gap on her enemies and the cool down is too long, she can benefit far grater from other keystones to gain damage.

Dark Harvest - This is nor a guaranteed way to get extra damage and since you will mostly be in mid lane against one other champ, you will only get 4 souls every large minion, provided you can get to the souls without the enemy killing you or taking damage, there are far better ways to get more damage.

Press the Attack - Since you will mostly be on your own in lane, you don't actually gain anything till AFTER 3 hits have already landed. most of the time you will just be using 'Q' and even if you land another hit, that's only three. this would only help you in team fights or if you used a combo of all her moves, in which only her last few would benefit, id hope to get a bit more damage in and more often.

Lethal Tempo - This one should be easy, Ahri is a mage so increasing her attack speed isn't going to help her take down enemies more effectively as nearly any other keystone, this is more for the ADC.

Fleet Footwork - so gaining movement speed and healing is good however Ahri already has access to these with her passive and abilities.

Grasp of the Undying - deal extra damage, gain health and adds health, why wouldn't you? there's a few reasons why. The only way Ahri could truly benefit from this would be to gain as much health items as she can to gain more damage, as Ahri isn't a tank you wouldn't be buying those items to get the added damage she needs. As for the healing, Ahri's passive provides her with health recovery. As she is able to be quiet agile, she would benefit more from damaging keystones.

Aftershock - Ahri relies mostly on her abilities which are ranged, there wouldn't be much chance for her to be close enough to a target without her being vulnerable to taking serious damage and that's only if you immobilize them.

Guardian - You will mostly be on your own in lane so you will have no one to guard to even use this.

Unsealed Spellbook - Using a keystone to change spells you chose because they work well, doesn't seem like a good investment, you chose them for a reason, would much rather the extra damage.

Glacial Augment - Slowing a champion can be great, but since you have to use a basic attack to do it, you wont get much damage in and since Ahri is ranged her slow will be reduced

Kleptomancy - Getting extra items or gold would be good and even if you don't want the items, they can be sold for more gold. More gold = more items = more damage. This is a slow way to get some added damage and doesn't really help you until you go back to the shop and the items are random so you cant rely on it to give you what you might need. It does help slightly but she would benefit more from early game extra damage to help kill enemies and minions for extra gold and pressure.