Farm as much as posible (obvious) and stay defensive for not getting harassed. Ofc you gotta get wards even though i did not put them in build and place wards when pushing or when you wants a gank. When you gets a gank or hits 6 you can hopefuly kill your opponent (noobs get owned earlier than 6). Also you want mana buff as early as possible for an extream poke possiblity by doing Command: Attack (Q) fast followed by Command: Dissonance (W) and some times you might even be able to make some dmg with a return with Command: Protect (E). And remember due to your passive you can easy farm without spells.

Orianna has a great farm potential so ganking isnt that big part of her gameplay.

Lets say you opponent moves toward bot lane and gets cought by a ward, just stay and farm and make sure that bot lane notifying the threat.

In this situation they are losing exp if the mid laners stays bot and they do not get kills while you might be able to get some free farm and then just camp a brush when their mid returns and kill him.

Before starting a teamfight try to make as much harass as possible then get you ball in and Shokwave your enemys. This will bring the more weak enemys drop to around 50% hp, and the gives your team a free fight with you having a ball flyin around that slows, deal dmg, shield, speed up team.

If you see that you have a bad teamfight team you might want to get teleport instead of ignite, it make you lose dmg but you can split push alot better.

If you see Kassa/Le Blanc you mostly want to swap lane with top/bot (if they have bad combo, but not to recomend). This will make you not get countered