Well played Orianna is a deadly champion. She does heavy damage, quickly clears minions' waves and can solo champion if you farmed enough gold. Remember that build above is not everything and it depends on game.

Greater Mark of Magic Penetration (magic penetration)
The only primary mark for mages. Your ball deals more damage with these.

Greater Seal of Health (HP)
Increases your survivability in early-game. You can stay longer in fight and buy necessary early-game items during first visit in base.

Greater Glyph of Scaling Ability Power (AP/lv)
Simply gives you more AP in mid- and late-game.

Greater Quintessence of Ability Power (AP)
Some AP to start with in early-game.

Of course it is not the only set of runes that will work.

9-0-21.

Offense tree increases your AP, reduces CDs and gives 15% magic penetration which is a great bonus.

Utility tree gives you some bonuses, most important are mana regen (Orianna is mana hungry), as well as useful CDR.

Remember to pick improved version of your spells!

WARNING: ITEM ORDER ABOVE IS NOT SO IMPORTANT, REMEMBER TO CHANGE IT IF NEEDED, READ BELOW

Starting items

I recommend:

This also will work:

Orianna need plenty of mana so don't start with Doran's Ring.
Meki Pendant gives you 7 mana regen / 5 seconds, Sapphire Crystal gives 200 mana, so Meki Pendant is better if you are in fight more than 2:30 after first ability used (in this time Meki Pendant will regen 200 mana). It's rather short time so it's not a problem to stay in fight for that time, but some players prefers Sapphire Crystal. It's up to you.
Use potions but don't waste too much gold for them.

Early-game items

Unless the situation is critical (low HP) try not to go back to base unless you have enough gold to buy Tear of the Goddess (600 G). If you can stay longer, it's good to be able to afford Boots (both items 950 G). Don't worry if you don't have enough mana, you can hit minions with autoattacks.
Why it's important to get Tear of the Goddess as quickly as possible? Because it gives you more mana as you use your abilities. The earlier you get it, the more mana you'll have in mid- and late-game.

Next items

The order of next items you buy varies. Here's what you need and why:

- CDR, attack speed
Orianna's attack gets stronger as she build AP (due to her passive, Clockwork Windup). Also, if you hit one target a few times, you get more damage each hit. That's why attack speed boost from Nashor's Tooth is useful. This item also gives you some AP and mana regen, always useful for Orianna. And most important is high CDR, 25%. With 9% with masteries, your CDR is 34% which is great bonus.

- survi
If you need more HP, buy this item early. It gives you 500 HP. Also 80 AP is great bonus. With Rylai's Crystal Scepter all creatures you hit with your ball will be slowed by 15%. Useful when escaping.


Everybody needs boots! These pair gives you 20 magic penetration. It's great bonus against non-tanky champions and minions. Less useful against champions with high magic resistance (if you don't know why look how it's counted). Warning: do not buy Ionian Boots of Lucidity! They gives you 15% CDR. It may look useful, but from Nashor's Tooth and masteries you have 34% CDR so with additional 15% you'll have 40% CDR (limit) and 9% will be wasted.

- AP
Gives you very much AP! Buy it rather in late-game, because it increases your AP by 30%, so it becomes more useful when you build some. Other items are more important than this.

- mana
It's upgrade of your early-game Tear of the Goddess. Mana collected by Tear will be transferred to this. It's another late-game item, because the more mana you have, the better it becomes, so it's better to gain much mana from Tear of the Goddess first. However, if you often Recall to base because you have no mana, buying Archangel's Staff earlier may help.

upgraded to - spell vamp
Hextech Revolver is good mid-game item. Buy it if you think you need some Spell Vamp (it heals you while doing damage with the Ball). For example, if you often lose some health and want to replenish it but not going back to base, Hextech Revolver is what you need. It also gives you some more AP.
Will of the Ancients is late game item. It gives you even more spell vamp and AP and also gives aura with this bonuses (useful in teamfights).

You can use different items than listed above.


Use it when fighting against mages.


Gives bonus HP and MP as well as helps fighting against mages.

Catalyst the Protector upgraded to
Gives HP and MP and restores then on level up. Although I don't like these items, some people prefer to buy Catalyst the Protector instead of Tear of the Goddess, and upgrading it to Rod of Ages.


It's good armor that increases your survivability. You revive after death so it'll rescue you near turret, but in other place enemies might kill you the second time unless they have low HP!


It gives some HP, AP and magic penetration. It's cheap and not upgradable item so buy it only if game isn't going to be too long.


Pretty useful item! It gives mana, AP, magic resist and movement speed. It's passive is also good - after using an ability (and you use abilities constantly as Orianna) your next attack will deal damage that equals to your AP (and you'll have plenty of AP).


If you're doing good in game buy this to get much AP. But if you don't kill much and die once in a while, sell it!


AP and magic penetration. Use if you like it.


Gives much AP but most important is it's Active. Not so useful on Orianna but pick if you think you can use it well.

CDR items

You don't have to use Nashor's Tooth, you can pick other CDR item. In that case pick Malady to stack with your passive. Here's some CDR items:
Plain boots with CDR 15%.
If you like active items, you may use it on champions as a fight opener. It also gives you AP and mana regen.
Gives more AP and mana regen.

Command: Attack
Your main ability. Level it up early, max it on lv 9. It does heavy damage to champions (may be used against single target). It also may help you quickly clear minions' waves.

Command: Dissonance
Creates a field that speeds up allies and slows down enemies. If Orianna has the Ball she can use it to go faster. This ability also hits enemies in the area of effect. Since Command: Dissonance has low range, keep in on lv 1 and until you level it up on champion lv 14-15, consider it as a speed modifier rather than harrasment tool.

Command: Protect
Almost as important as Command: Attack. It does the same but requires allied champion or yourself as a target. Command: Protect gives also as shield after use. If you learn to use it quickly, you can shield yourself of ally from damage you know will come, e.g. Karthus'es ulti, turret hit.

Command: Shockwave
The Ball pulls the enemies, it disables them for a moment. Most people don't know that if enemies are pushed against wall they are stunned. This command should be used only against champions, don't waste it on minions! Read more in the next chapter.

If you like, replace Q > E > W order by Q > W > E. They both are good.

Orianna may use some useful combos from her skills.

Against minions
Q - E - Q
or: Q - W - E - Q

Escaping
E - W (repeat while in safe place)
If you have your ulti ready, use it. It may seem as a bad idea (it'll pull enemies to you) but they will be disabled for a moment, then you can use W - E to run. With a little of luck, the enemy will have this low health after your ult that he'll stop chasing you.

Quick champion's harrasment
Q - R - W - E, then Exhaust if possible to finish champion with Q - W - E, repeated if needed.

If you're in base use following skills:
Q in direction where you're going to go, then W. You'll get speed boost going through field of W, it'll be free because in the base your mana will replenish instantly, and from Tear of the Goddess or Archangel's Staff's passive you get extra maximum mana.

I recommend:
escaping, especially through walls
disabling enemies when escaping or killing
These spells have their improved version that you can pick without problem.

Other useful spells:
jungling (Orianna is a good jungler with her protection)


Don't take this:
You can go faster with Command: Dissonance...
Good lifesaver but Flash is better...
Long cooldown makes is useless...
Not enough to resolve problems with mana in early-game, and totally useless in mid- and late-game when you build mana...
Nobody recommends it, it's useless...
Only for supporters...

Runes
Main runes are AP and AP/lv (both types) to give you much AP in early-, mid- and late-game.

Masteries
9-0-21. Offense - magic penetration, CDR, AP. Utility - mana, mana regen, CDR. Improve spells.

Items
Start:



Early-game:


Core items:
if you need CDR or use much autoattacks
if you need more survivability
if you want to buy better shoes
if you want to build much AP
if you need even more mana
if you need spell vamp
if you want to upgrade

There are also other good items.

Skills
Q > E > W or Q > W > E. Practise your combos.

Spells


and for jungling.

Good luck!