I make a new thing called Orianna Spam Ball, this make you have your skills allways avalible, and make a high damage, remember oriana is not a nuker mage, and she can be a good support in turret killing and team fights

you start the game buying a dorans ring, a good start item i think, and your first skill are command: Attack, and you think, how i can recover my ball?, simple, get out of the range of the ball and you recover your ball, cuz if you cast Q again, the ball only get moved from the current possition to the marked position, thsi problem can be solved when you get E skill

you can have troubles of mana untill you get tear of goodness, in that case, each time you use an ability, you are raising your mana, that was good cuz you have more mana to spam abilities

you keep getting mana all the time that take you get the rabadons and the Morellos, at this point, with the nashor you max your colddown(40%)

the next steep is get an archangel staff, and all the mana that you get spamming abilities with tear of goodnes are fused with archangel staff, making you get a lot of AP at this point, and you get the 2 last items that are rod of ages and void staff

Your real ap(yeah, the AP showed in the build didnt count the 3% of your mana, the 20 extra AP of the rod of ages and the 30% that give you the rabadoons) is the next at lv 18 with full equip:

3.06 x 9 = 27.54 (rune AP)+
155 (rabadoons)+
55 (Nashoor thooth)+
45 (Archangel staff)+
80 (rod of ages)+
70 (void Staff)+
20 (10 min of rod of ages)+
3225 x 0.03= 96.75 (bonus at top mana by the archangel staff)=
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549.29 x 1.3 = 714.077 (30% bonus by rabadoons)

a realy good ammount of Ap that make you hit hard, and make your shield be very useful to protect your teamates in team fights, your shield can cover over 600 Damage

with a good amount of AP, your farm abilities are realy increased, making you ear a good source of money with your minions

Your ulti in team fights are very useful, you can make all the enemy champs go to a unique place if they are in the AoE and stun then for 1 second, in that time, was the oportunity to your teamates to kill teh most posible amount of enemies, ahd you can still supporting your team withnyour shield and your ability to Slow the enemies

This is my explaniation, i hope you glad the build, pelase coment and vote if youre ok or make a suggestion =D