this guide is nice, but I disagree with the will, otherwise I think it is good.

I agree with just about everything Throatslasher said, but would like to add that Will of the Ancients is not a good item choice on Orianna. The item only gives you 1/3 of the spell vamp percentage it would normally give for AoE moves. Since all Orianna's abilities are AoE, you benefit far less than someone like Ryze might, since two of his spells are single target.

Also, you say orianna has a poor laning phase, but I disagree. I think she has an EXTREMELY DOMINANT laning phase against a lot of matchups. She is the HARD COUNTER to gragas.
she crushes:
Ahri, Karthus, Gragas, Fizz, Cho'Gath, Veigar, Syndra, Swain, Kassadin, Ryze, Casseopia and katarina, in my opinion.

I would love a matchups section talking about how to play her vs certain champs.

95% correct, but you made some major mistakes. 1st, it's important to max a skill with orianna at level 9. Most people prefer to max Q, but I personally prefer to max W. It doesn't matter which, you have to max one at 9. In rare circumstances, you can put an extra point in protect, but you should still be maxing a skill by level 9.

Second, in masteries, why would you take improved recall over enhanced flash?

Third, in masteries, why would you take 1% damage and 1 ap over 3 attack damage? Orianna gets so much utility from auto attacks and her passive. I've won many lanes because of using my auto-attacks to completely outtrade my opponents. I'd say orianna is one of those rare champs where the 3ad is almost mandatory. You can choose to put the 3 points in ap, or the 3 points in havok, your choice.

I like this guide, I will try this out

Sweet :)

Yeah i actually managed to get a 14/4/17 with this build.