Alright so this is the first build I'm ever making, I hope you guys like it. Please try it out before voting it down hahah! And if ever there are some flaws,(and I'm sure there are,) please point them out, but don't be too harsh on me. :D

Alright so as you can see, I chose mainly magic penetration runes for Orianna, so as to compound with the magic penetration that you'd get from the Sorceror's Shoes and Void Staff. I also got magic regeneration runes because my item build doesn't exactly provide for much mana or mana regen early on, at least not 'til you build up your frozen heart.

For the masteries, it's just your basic 9/0/21, pretty common for AP heroes like Orianna. Again, the 15% magic penetration from the Archaic Knowledge will be pretty painful. With just that and your Void staff that's already 55% magic penetration. Your skills will burn through just over half your target's magic resistance. Pain? I think so :D

- Boots of Speed -
I chose this as the first item instead of a Doran's Ring because aside from the movement speed it gives, which isn't really useful early, it brings you to your Sorceror's shoes faster. Which means that you get to your Magic Penetration faster, which is the point of the build. Just grab 2 health potions and 1 mana potion and you should be good for awhile.
-Rod of Ages -
Rod of Ages should be bought early on, so that you could get it's maximum benefits earlier on. It's effects grow every 1 minute, capping at 10 minutes. It gives a good amount of health and AP and should make sure you're not too easy to kill.

- Void Staff -
40% magic penetration. 70AP. Since this build is focusing on magic penetration, I think the item pretty much speaks for itself. :)

- Rylai's Crystal Scepter -
This item is really good, albeit it takes awhile to build up, however I believe it's worth every cent. Rylai's Scepter provides you with more health, to take the edge off Orianna's squishiness. (she's quite squishy.) it also provides you with an 80AP boost and on top of all that the 35% movement speed slow will secure you even more kills.

- Rabadon's Deatcap -
To be blunt, any self-respecting player looking to build his AP would want this item. An insane boost in AP, (140AP) and it's unique ability gives you a beautiful 30% additional AP. You should be a train of pain by the time you have this item, along with all the magic penetration you have. By now, you should be able to tell which side has the upper hand. This should tip the scales in your favor. ;)

- Frozen Heart -
I actually couldn't decide on which item to get, so I thought of what this build was still missing. I decided on an item that would provide mana and cooldown reduction. So this item is pretty good in terms of that, plus it gives you a nice bonus of 99 armor to make you less vulnerable to physical attacks.

- Zhonya's Hourglass -
This item is actually very useful and could save your *** or turn a fight around if used correctly. It gives you a 2 second break from pain and suffering in a clash, and could be used to stall your enemies until your skills are ready again. Every second counts. I for one cannot remember to activate this to save my life. (Literally)

- Abyssal Scepter -
The Abyssal Scepter gives you a good boost in AP and a great bonus in magic resist as well as a small push in the direction of magic penetration. You could work this into your items somehow if you really want more magic penetration, but it doesn't really attend to Orianna's squishiness as much as the Rylai's, and not nearly as much AP as a Rabadon's.

- Lich Bane -
Lich Bane gives a good boost in AP, not to mention the effect it adds where after casting a skill your next attack deals bonus damage based on your ability power. This coincides greatly with your innate ability, which also gives bonus damage based on your AP. A good item to consider.

As you can see, this build is an offensive type, and so I chose to get Protect much later on. In my opinion getting one level of Protect at Level 4 would be virtually useless later as opposed to getting another level of Dissonance or Attack. Sure, the shield from Protect could save your teammates or even yourself while you're under siege, but why not just build yourself in a way that you could fight back instead of run? You could kill the enemy hero chasing down your teammates or the one chasing you down.

At Level 3 your Attack should be strong enough to harrass your enemy enough that they can't ignore it. Seeing as your mana reserves aren't that high, you should conserve your mana and steadily bring down his health, then come in with a Dissonance, and if necessary, Flash, Ignite and just auto attack. At around Level 3-5 it isn't difficult to kill someone. Take note however, if they themselves have Flash, or even Heal.

Well first of all, Even though Flash has a relatively long cooldown, it's a great positioning skill. If you're not too good at aiming and timing Orianna's Command:Attack skill correctly, and are still practicing, then you could just Flash right up next to your enemy and use Dissonance or Shockwave first.

Flash is also a great escape mechanism, because you can use it to place a huge gap between you and your enemies, which could buy you more time, or to pass through walls to freedom and safety. :D
Now, Ignite is a great DPS spell which secures your kills. You'll almost never have to deal with enemies escaped with just one or two hits worth of HP anymore. (But on the downside, if they do escape with that much health, even after Ignite, you will be even more disappointed than you would have been if you didn't use Ignite. :P)

And in early game, this skill can really turn the tides when you and your enemy are trading punches. This could be the reason you got that first blood and extra cash, bringing you closer to your items, and if constantly used correctly, can seriously hinder the growth of the enemy heroes, and contribute to your own growth immensely.

Alternate Spells

Ghostwalk is also a great escape and chase mechanism, however it just doesn't allow you to position yourself as well as Flash does.
Exhaust could also help you secure kills, especially if you decide to lane instead of taking the mid-lane. It would work well with and keep your teammates in range of the enemy heroes.
Clarity is actually a pretty great alternative because it fixes your mana problem. With the build itself, I find myself going back to base quite often and having to bring along a number of potions, but this is without the mana regen runes.
Teleport isn't as good as the other spells for this particular build, but it is still a plausible alternative, since you'll be going home often for health and mana.

Don't even think about getting these.Why would you get Revive when you could get a spell that could prevent your death altogether? Useless for Orianna in my opinion.
I pray for you if you even considered getting this spell. I mean, seriously. Think about it. Will this reeealllyy help you?? XD
You're not going to be jungling. Orianna can't even jungle to begin with. If you have problems last-hitting, practice. Don't resort to this. You won't learn to last-hit.

Early Game
You're gonna want to grab mid. With this build, you're trying to progress your abilities and get your items as soon as possible. Orianna unlocks her full power that way. Just focus on last-hitting until around Level 3, where you should start to work in a few harrasses with your Command:Attack. You can also use that skill if you're having trouble with the last-hits.

By Level 4 or 5, if you harrassed well enough, your enemy lanemate should have about half of his HP. You can attempt to kill him by using your Command:Attack, then Dissonance, then Flash up next to him, Ignite, and try to hit him as much as you can. At the very least, if he doesn't die, you've managed to push him out of lane. That would give you a slight exp and gold advantage. At the very least that is.

Don't try to gank until around Level 8 or 9, or when you have your Mejai's and Sorceror's Shoes. Focus on trying to destroy your enemy tower, and killing your lanemate. You can gank the other lanes however, if your team isn't doing too well and needs an extra hand. Don't be too afraid to help out. Make sure you have your Shockwave at the ready when you do though, because a failed gank just means you lost precious time that could've been spent doing something more efficient, such as farming or pushing.

If your enemy hero is dominating your lane; which doesn't happen quite often because Orianna's Command:Attack is very spammable, has great range, and decent damage, then try to ask your teammates to help out. With the bushes on either side of the middle lane, ganking there isn't too difficult as long as your enemy is closer to your side of the lane. This build relies quite a lot on your performance during the early game, so make sure if you can't kill, at least don't die.

Now if you're laning with a teammate, try to harrass the softest hero as much as you can, and make sure to make him your target. The same thing applies: by Level 4 or 5, one if not both of your enemies should have a relatively low health, the threshold of your enemy's HP for a successful kill should be higher than if you were trying to kill an enemy alone, because there are two of you, therefore you have twice as much skills, spells, and damage.


Mid Game
Mid Game happens by the time you're around Level 10 or 11, or you've broken your lane's tower. Hopefully by now, you have your Sorceror's Shoes, Mejais, and if you've done well, Void Staff. You should be ganking by now, and securing the Dragon. 190 Gold for your whole team is an insanely great advantage. That's just 50 gold shy of 1000 gold split amongst everyone. You should have at least 4-6 charges on your Mejai's, and just roam around, focus on taking down enemies and push the first towers. If the opportunity presents itself, push the enemy's second tower. It provides a plump sum of 150 to your whole team, which is almost as good as killing the dragon. If your enemy has a jungler, make sure to try to ward their jungle and counter-jungle to starve him of creeps.

Clashing should be more common by now. Your role in clash is either to initiate with your ulti, or to surprise your enemies with it and turn it around completely. Orianna's ulti is, in my opinion, the most useful skill in her arsenal, not just because of the damage it deals, but it's range, as well as the fact that it knocks all affected enemies into the air. You shouldn't be charging in like a maniac. You're not Tryndamere. Just stay at the back and aim your Command:Attack and Dissonance correctly, and if you're losing the clash, provide retreating fire and use Dissonance to help your teammates escape while slowing your enemies down. Your role is to bring your enemies lives down. Don't be too discouraged if you can't kill in clash, after all that's the point of Mejai's. So you don't fall too far behind your teammates if you can't get any kills.

I have less to say about Mid-game than Early-Game because this is when strategy and tactics start to come in. In early game, theres a correct way to start off, but in Mid-game, you and your team are the ones who decide what to do. If the enemy team's line-up is full of carries like Cait, Trynd, Master Yi, etc., then make sure to end the game as soon as you can. If the enemy's line-up is full of AOE heroes, then try to hunt them down one-by-one. LoL is a very situational game and what you do during mid game is varies on a case-to-case basis.

Late Game
Now for Late Game, hopefully you already have most of your core items. The plan is simple. You should start sticking to your team like glue, and keep the dragon and Barron warded. Knowledge is power. The more you know about where your enemy's are and what they plan to do, the more prepared you are to kick their ***es back to their mother's wombs. Wards are inexpensive and if placed correctly can win you clashes more than once.

Just make sure you stay behind your teammates. Orianna is very squishy and if you've been owning the enemy like this build allows you to, then they'll want to kill you first. Just come in with a Command: Attack, Shockwave, Dissonance, and by now you'll have protect so use it on either your carry or tank. In other cases, you may want to use it to save your teammate's skin as well.

If you manage to keep at least 4 out of 5 of your heroes alive, and managed to kill 2 or 3 of your enemies heroes, take advantage of that and push. However, this isn't an absolute thing. Your creeps may be too far from the enemy tower and there might not be enough time for it, so don't try to risk it, lest you lose a clash. Again, it all depends on how your team wants to play it. Offensive or defensive.

So that's my build for Orianna. Again, if there are any discrepancies that you find in the build, please inform me and I'll be sure to change it. :D I hope this build helps you play and understand Orianna better. I'm no expert on Orianna, but this is my way of playing her, and I'm simply sharing. Please try the build out before voting down.

And lastly,

Thank you for reading my guide :D