There once was a Piltovian man named Corin Reveck who had a daughter named Orianna, whom he loved more than anything else in the world. Though Orianna had incredible talent for dancing, she was deeply fascinated by the champions of the League of Legends. This fascination compelled her to begin training to become such a champion. It is unfortunate that her sheltered, wide-eyed naivete led her to take unnecessary and dangerous chances which ultimately led to her tragic demise. Orianna's death shattered Corin, driving him into deep depression and an obsession with techmaturgy. He could not stand the void his daughter's death left in his life, so he decided to build a replacement - one that would complete Orianna's dream of joining the League. What was created is the clockwork killing machine that Corin named after his daughter. Knowing that she was destined to be a champion and seeing the way the times were changing, he created The Ball as her pet and protector. This nearly symbiotic creation uses a different type of techmaturgy, relying more heavily on electricity than clockwork. Orianna and The Ball now fight as Champions in the League of Legends, using her sometimes misguided morality as a compass. She tries in earnest to fit in with those around her. However, no matter how hard she tries, Orianna can never be human and there is always something unnerving and alien about her. Though she attempts social interaction with other champions in the League of Legends, there are few who can get past her exotic nature. To many, it's as if there's nothing inside, that Orianna is just a soulless clockwork shell - a dangerous and deadly one at that. However, all along she remains the perfect daughter in her father's eyes. ''Dance with me, my pet. Dance with me into oblivion.''

Orianna is a very special caster and can do great damage while also supporting her aliies.
Orianna's best spell combo is Q→W→Rhttp://www.solomid.net/guide/skills/orianna/r.png → W http://edge2.mobafire.com/images/ability/orianna-command-protect.png on yourself.
Explanation: The Q spell is the combo initiator, the W spell is for slowing the enemies, the r spell is to kick the enemies begind your ball and E to damage the enemies Before giving a nice shield to yourself.

Clockwork Windup
Orianna uses her ball as a focus for her spells and attacks. Orianna's ball automatically returns to her if she is too far away from it.

Orianna's autoattacks deal additional damage plus 20% of her Ability Power in magic damage. Subsequent attacks against the same target within 4 seconds deal an additional 15% magic damage. This bonus stacks up to 3 times.
This is Orianna's passive ability and can deal great amounts of damage in early game.

http://edge2.mobafire.com/images/ability/orianna-command-attack.png Command: Attack
Orianna commands her ball to fire toward a target location, dealing magic damage to targets along the way (deals less damage to subsequent targets). Her ball remains at the target location after.
This is Orianna's main skill. Without this skill Orianna could not deal any damage.


http://edge1.mobafire.com/images/ability/orianna-command-dissonance.png Command: Dissonance
Orianna commands the ball to release a pulse of energy, dealing magic damage around it. This leaves a field behind that speeds up allies and slows enemies.
This is Orianna's main damaging ability. It gives a decent slow to enemies and a nice speed buff to allied Champions.


http://edge2.mobafire.com/images/ability/orianna-command-protect.png Command: Protect
Orianna commands her ball to attach to an allied champion, shielding them and dealing magic damage to any enemies it passes through on the way. Additionally, the ball grants additional Armor and Magic Resist to the champion it is attached to.
Command: Protect it Orianna's main support spell. It gives a pretty strong shield and lasts as long as you are in range of the shield's target.


http://edge2.mobafire.com/images/ability/orianna-command-shockwave.png Command: Shockwave
Orianna commands her ball to unleash a shockwave, dealing magic damage and launching nearby enemies towards the ball after a short delay.
This is a nice spell to collect the enemies on 1 playce to hit then with spell shots easier.
Its very nice in combination with Miss Fortune's Ultimate ablility.

For runes i use:
Magic Penetration Marks http://static.leaguecraft.com/images/icons/runes/rune_36.jpg .
Mana Regeneration per Level Seals.
Cooldownreduction Glyphs.
Ability Power Quintessinces http://edge1.mobafire.com/images/rune/greater-quintessence-of-potency.png .

I use 9/0/21 Masteries here is a picture of my masteries:

First of all its best to play Orianna pure AP with some Health Items for some survivability.
Your starting Item is Doran's Ring http://lolers.de/images/items/1056.gif .
It give you some nice starting AP in combination with the Mana Regeneration and Health.
Your next Item is Boots of speed http://lolers.de/images/items/1001.gif .
A Magic Wand and Sorcerer's Shoescome next.
Your first big Item should be the Rod of Ages. It gives you some nice Health and Ability Power.
Rylai's Crystalscepteris nice because it gives very much Health and Ability Power.
Now you need more AP, it's best to buy a Rabadon's Deathcap because it gives SO MUCH AP.
Your last Item is Shurelias Revery, because you dont need AP anymore but some supportability is very nice to chase or run.

As Summoner Spells I use Flash and Ignite.
Clarity and Teleportation work great too but it is your choice and mostly it depands on your team.

For farming you need Sorcerers Shoes and Rod of Ages.
You first use your Q spell to hit every creep in the wave. Then you use W to kill the caster minions and last you hit the melee creeps with 1 AA on each then use your E to kill the melee minions. This gives you the most farm.