First off, some BBCoding would really help in making your guide look appealing. I recommend taking a look at this page.

Now about the guide itself. Your starting item(s) have good intentions, but Ahri's base movespeed is insanely slow, so starting boots and health pots could really be more beneficial for escaping deaths early while laning. As long as you use your spells in moderation at the beginning of the game, you won't be strapped for mana before you can grab a blue buff, and all the AP from your runes means that a Doran's Ring won't help much, so don't even consider it.

You also probably shouldn't grab a Sheen early on, as it won't give nearly as much AP as other, more effective items for Ahri will, and the passive is useless on any AP. You should delay the Sheen until right before Lich Bane, since you won't be able to put it to any good use, so you might as well have for as little of the game as possible.

Lastly for items, a Hextech Gunblade won't be much use to you. Might as well build your Hextech Revolver into a Wiil of the Ancients instead, as it will give more AP, and survivability.

With you masteries, as the others here have already said, you can give up 1 AP from Mental Force for 5 AP from using Ignite if you just put the point in Summoner's Wrath instead. Also, you always want Runic Affinity. It's the only worthwhile thing in the Utility tree for AP's.

I would also like to recommend that you max your Fox-Fire second, as you'll get more from it's extra damage than you will from a slightly longer CC from Charm, but it's up to you. Also, getting a Hextech Revolver before your Rylai's Crystal Scepter could be better for early survivability, as it will give more AP, and costs much less, but again, it's all up to you.

I hope this all helps, and don't worry, we're all new to guide making at some point!

For both of the first two replies, like i said, the mastery build is for ability power per level. I also havent learned to put in all those silly pictures and such. It's my first guide on this site. I am a big aggressive poker and either dodge their attacks or swap out with my lane partner if i get a little low on health. Ahri is already extremely squishy, that's why you poke with orb of deception. Also, the last three items are optional and the slots are used to adapt for who your'e fighting. I buy sheen for the mana because I was running out fast in early game, and the AP is a good starting amount for extra damage. I have the spellvamp on in the masteries because I don't see anything better for ahri, and as stated in the guide, the hextech is optional.

You have a good start on this build, but you could really use some mobafire coding with your runes/masteries alongside better explanation. I kinda like the idea of spell vamp, but it's not as useful as a stat for Ahri. I would build more offense, play a bit smarter, and you will not need spell vamp.

This is a good start for a guide, give more detail and possibly re-think spell vamp.

-1
Your build makes her too squishy in eraly game. You should start with Doran's ring or Boots +3 pots.

Your mastery is a nonsense. If you use Ignite, then why you didn't put a point to Summoner's Wrath from Mental Force? Deadlyness??? It's easy to last hit with her, so you simply don't need it. You already put a Sheen onto your build, as an AD steroid (IMO you should buy it later, better focus on early Deathcap or Rylai's Scepter). No Runic Affinity? You benefit lot more from +30 secs. of blue or red buff, or +48 secs. of Nashor's buff than from 1% Spell Vamp.

Hextech Gunblade? It's ok that you want to secure a kill, but for f*cks sake, NO.

Better remake the whole guide. The composition s*cks, and there aren't any informations about your goals, teamfights etc. And please, if you make a guide, don't be lazy to put in icons or some screenshots.

Sorry for my bad english, it's not my native language.