Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
UPDATE: Made things slightly less ******ed. The theme of partnering autoattacks with the ball remains, but the lack of Lich Bane and Clarity improves things 98%.
To whomever you are: greetings, and welcome to my first ever build / guide on this site. I'm still learning all the intricacies of formatting, so forgive me for not using that many pictures and the like, but bear with me and hopefully it'll help you nevertheless.
The premise behind this build is simple: combine powerful auto-attacks with the various abilities of the ball. Positioning is, of course, key, but the real power behind Orianna lies in her passive. Balancing both AP and AS allows for Orianna to develop into a formidable auto-attack champion, while doubling as an unparalleled support mage.
NOTE: As with any build, you shouldn't take the build order, ability order or exact item in the build as strict fact. Always exercise flexibility, and see the Items guide for more details.
Orianna is probably the deepest mage in the game, in terms of gameplay. The key to her playstyle is position of the ball, both in relation to teammates and enemies. If one of your teammates is leading a chase, use command protect followed by command dissonance to speed him and everyone else up. Is a teammate on the other side of an enemy? Use command protect to send the ball through them. Send the ball one way to set up another shot after Q cools down.
A few basic combos are thus:
The Sweep: Send the ball through a wave of minions or enemies, then immediately cast Self Command Protect to bring it back through.
The Yoink: Use Command Protect on a charging teammate, then Command Shockwave to bring the enemies towards him. Follow up with Command Dissonance, and suddenly they are slowed while your teammate is sped up.
The Escape: Use a mixture of command protect and command attack with command dissonance to lay dissonance patches where it will speed your team / slow their team up / down the most.
The Houdini: When being chased, hide in a bush. When your pursuers are about to enter, use command shockwave and command dissonance as you run the other way. They won't be able to follow.
It's important to keep in mind that shockwave will always bring enemies together near the ball, ending up on the opposite side to where they started. Therefore, it would be unwise to use shockwave if escaping if it would bring the enemies closer to you.
Of course, simply commanding the ball isn't enough to fully utilise Orianna. And this is where Clockwork Windup comes in.
Items / Explanation
Orianna's passive is simple: Her attacks deal bonus magic damage, and that magic damage increases with each subsequent attack up to three times (i.e. four increments of magic damage). The magic damage also scales with ability power. At its most basic level, this means that AP is, essentially, converted into AD. However, as it is specifically magic damage, it relies on your magic penetration and an enemy's magic resistance stat. This is where Malady and the Sorcerer's Shoes come into play.
Malady is a cheap, wonderfully useful item. It gives attack speed, additional ability points, and has a unique passive of reducing an enemy's magic resistance by up to 24. Most champions have a base stat of 30. combine this with the MP of your shoes and runes, and suddenly your auto attacks begin to hurt. not only that, but lowered MR is a benefit to everyone in your team, making Malady perfect for early teamfights. And, of course, The Ball.
Following Malady, one should try and get a Tear of the Goddess. This will allow you to ween yourself off the blue buff. Next, go for a Rabbadon's. The deathcap adds a tonne of AP, which is ultimately the main thing Orianna needs, while the Archangel's Staff helps add slightly more AP. Finally, depending on the focus of your enemy team, you should either go for an Abyssal Scepter or Zhonya's Hourglass, or perhaps a Guardian Angel in the case of even teams. Shoudl the game draw on for too long, consider selling malady for another Ap item - auto attacks won't be quite so viable much later in the game.
Summoner Spells: Flash is a must for a movement spell as you already have something of a ghost / exhaust effect from Command Dissonance. Ignite pays dividends throughout - Orianna's inherent lack of sustained DPS means enemies will often escape with a little health left. Not to mention ignite reduces enemy magic resist, aiding Malady to no end.
Runes: Magic Pen runes help with chipping that little bit more off an enemy's magic resist, AP and mana regen runes speak for themselves, and health runes help a lot in early game. However, feel free to use movement speed runes instead.
Skill Sequence: This is very flexible. Bear in mind that Command Protect's mana cost doesn't increase as you upgrade it, while Attack and Dissonance do. If you're side laning in early game, or are facing a particularly aggressive enemy, you may want to consider upgrading it sooner rather than later.
Orianna is best played when positioning both her and her ball appropriately. Consider them as two half-champions in their own right, and you'll be a devastating force on the battlefield. However, while she can certainly out-damage other champions, her squishiness is definitely a problem in any confrontation. Use command protect to counteract this.
Your role with orianna is to support first, kill second. Assuming you do end up getting a soul stealer at full stacks, your shield can give upwards of 800 temporary HP. You'd do much better to stay alive and keep everyone else in top condition rather than dying to take down one or more of the enemy.