Personally, I really enjoy playing Ahri. I main her (with around 250k mastery points at the time of writing this, and with the other two being Jinx at 200k and Ezreal at 150k Mastery Points, so I know that these 2 ADC's can work very well with Ahri Support), and she is one of the only midlaners I find enjoyable to play game after game. I decided to try and see if I could make her work in other lanes, and I already knew she can be picked as a support, so I tried to look further into this by trying out different builds and runes to see just how much of a support I could make Ahri, while still making her a good pick and not completely useless. Obviously there are other picks that are way better than Ahri in support, but this was just for me to have fun as Ahri in another lane while still being able to do something, so I decided to share it incase anyone else felt the same and wanted to be able to enjoy Ahri in another lane other than mid!

In midlane, her Charm is already very useful in allowing Ahri to work with her jungler and focus on feeding her jungler instead of herself so that they can help other lanes more effectively and overall do their job as a jungler easier. I already run a CDR based build midlane which I prefer now over the Ludens -> Horizon Focus Build I used to run, and I try and play Ahri in a more support way midlane now too which I have found to work better and help games go smoother. Taking Glacial mid is something I hate doing and I do not think it is worth it, however as support, you do not really want to have high damage as you want to focus on getting your ADC fed. Getting a few kills is fine, as it helps you get to your Everfrost powerspike quicker, however running something like Electrocute as support is still viable, but sometimes the electrocute damage is enough to steal a kill which may have been first blood to your ADC. Going Inspiration also allows you to run Future's market, helping you get early items more efficiently and can also help you get a few control wards too that sometimes you might not have been able to afford if you didn't run future's market. Cosmic Insight also helps a lot, as it reduces your Ignite, Flash, Everfrost and Redemption cooldowns, allowing you to have more opportunities to get easy picks and also heal your team a bit more often than you could without it.

I also run Sorcery with Manaflow Band as this helps with Ahri's mana usage later on, and with Transcendence, your cooldowns will be even less earlier on too before you get all the CDR Items. (Going CDR in offense too instead of Adaptive force or Attack speed also helps with this and it is what I prefer going on Ahri Support)

Going Redemption gives good CDR and also allows Ahri to heal her team, as well as getting extra healing herself, which is something I like. Vigilant Wardstone is also very good, as it's passive gives you a lot more health, AP, and increases your ability haste by quite a lot. It also helps you maintain your vision control on the map by being allowed to place one more Ward and Control Ward, as well as having Oracle and holding more Control wards.

Overall, CDR on Ahri is quite strong already midlane, so I took that into account and tried a complete full CDR Ahri in Support where the lack of damage wouldn't matter too much as, while the build still does do damage, your main goal is to get the ADC and your team easy picks and feed them to get a lead and win the game.

With Ahri Support, You want to look to max Charm first as it is what makes you viable as support, and levelling it reduces the cooldown on it as well as increasing it's duration. However, doing this will mean you lack damage from your Q, so you can put 2 points into Q earlier to increase the damage of it a bit early and allow for more Q Poke damage.

Going W first is something I have been trying recently and I do find that it works better for my playstyle than going Q first. However, it is all up to personal preference as it does not matter all that much which of the two you go first at level 1, as long as you can poke it is fine.

At level 6, Ahri gets her big powerspike due to her ult and having the high mobility, giving her a lot of opportunities to have a good engage with an Ult + Charm, especially if your charm has been levelled 3 times already, increasing it's duration.

Shurelya's is probably my 2nd favourite build on Ahri Support, and it works with Glacial if you want to focus on staying in lane as well. The electrocute rune page is focused on a more roam based play style, helping out other lanes and getting vision in their bot and top jungle when your ADC is not present in lane, or is playing safe. Rushing Boots of Mobi here lets you get early and unexpected roams to midlane if the lane is pushed under your midlaners turret, allowing them to get ahead with an easy pick if you hit your charm successfully. Rushing these boots also helps you get early deep vision as well.

The moonstaff build is my least favourite on Ahri support, and I don't think it is really that effective anymore after Moonstone got changed a little. However, the build still does work and can be fun to try out.

The Full Burn and Slow build is also very fun to play with, and you can use either Glacial or Comet with this as both can work pretty well with the items. Since you have no actives, you don't really need to go Cosmic Insight, which is why I prefer going Sorcery when I plan on using this build.