Orianna already gains so much from the transition to late game it's frankly not necesary. If you were to buff anything at all maybe you could do a bit for her early game, but a good Ori knows how outplay any lane opponent.
In late game her AP scalings make the QW chunk 60+% of their carry's hp, your shields start to become quite fat, and that Ultimate can single handedly win you the game.
She scales hard and her builds are already highly flexible for a mage. If you want to hit more ball shots, you pick up the minimum 20% cdr she needs to function or put it on amumu who will make your ball the fastest deadliest thing on the field.
4 lyfe