Well its my first guide so dont be to rought on voting it (Constructive criticism does not include).
Orianna it's first champion which has such a unique gamestyle. She's very hard to master and play but she can radically change the teamfights due to her CC's. This build works for me and it can work for everybody who now's how to play in team . Don't vote it down only because you cannot win due to your skill ;p

Note: Orianna is mostly a support char , that mean's you usually will get more assists than kill's and you will be saving your teammates rather than killing enemies . She can be very nice help to your team which can change the results of teamfight and even all games but yet not for geting pentakills and soloing feeded champions. Some ppl can consider her weak for her low damage but you have to remember that shes not a dmg dealer - shes a SUPPORT !

Well runes are the thing that im working on actually . My choice are:

red:Magic penetration - self explanatory
yellow:Ability power or Armor - it's your choice and it depends on your masteries - when going more into offense change them for armor otherwise buy armor as orianna is an Megasquish :D
blue: Ability power - a little burst that you need on laning phase to make harrasing easier
The big ones - You can go for what you want depending on your playstyle ;)

The must for orianna (if you are using my build) is Clarity . Even with the meki's pendant she's very mana dependent and if you want to farm well staying till level 8 or 9 without going back clarity is a must .
The second one : My choice is flash as it's a very nice escaping tool , you can also use ghost but i dont find it so usefull even for chasing . You can also take ignite but i won't recommend it as Orianna is very very squishy till she gets RoA and in the beggining she is not geting a lot of frags.

Items:
Let me explain my choices :
Tear of Goddess- That should be the first item you get after you get your boots, this little item make's your mana pool grow every time you use a skill . It caps at 1000 mana and it takes quite long to accumulate it so im geting it asap.->(reference archangels staff)
boots of swiftness: That boots are created for her . With the flash , the ball acceleration , and those - Orianna is an escape master . You dont need magic pen. as you get it from runes and masteries , the tentacity is also useless for her.
Rod of Ages:Another item to get asap . It gives you everything - health , mana(that later converts into AP), and AP over time , making you stonger each minute . That's the most important thing of her build.
Guinsoo's Rageblade: Another perfect item for her , gives you ap,ad and as. Someone can ask why does she need Ad & As, the answer is simple : You dont only rely on your ball and her burst dmg. Geting orianna's atack better you are converting her into serious danger and potential squishy assasin :D . Moreover guinsoo's sticks very well with your passive and after a while you are geting 48 Ap and awesome atack speed - the ball make's it even easier as you are atacking and spellcasting at the same time . That's very good item as it gives you everything that clockwork lady need's.
Wit's End: Another item that this time give's you a very serious atack potential. You can get all the stack's from your passive , Guinsoo's and Wit's in no-time and make a life of someone real nightmare.
Archangels Staff,Rabadon's Deathcap : After elevating your basic atack it's time to take care of the ball which uses AP and it's your main source of dmg and protection for your allies ( Orianna is mainly support char rather than assasin). At late game the mana from tear of goddess and RoA It's used with the archangels staff to produce you a lot of tasty ability power . More than that : Your rabadon's will take it even further making possible to you reach nearly 600 ap .

With that items you have everyting orianna as a support/burst dmg/dps/*escaper needs : Moving and Atack speed , AD , AP , some health ,some CD reduction , and BIG mana pool to spam your ball in all directions.

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