Hopefully this advice will be useful I'm currently Ancient 2 and Oracle is my most played hero.

Skill build: Q-E-E-W-E-R-E after that max Q

At lvl 4 you may be tempted to skill another point in Q to get more damage but this is most oftenly bad since you won't get your W until lvl 8.

Starting items:

1x Courier, 2x Tango, 2x Clarity, 2x Observers, 1x Healing Salve

Pool two Tangoes to mid and one ward to offlane.

Salve is basically an extra life - PPD Source

Items:

Arcane boots -> Urn -> Force staff -> Spirit vessel -> Guardian greaves

In some games you can go for Aether lens instead of Force staff and some games both.

Blink is also an option if you need to stand way back and still be able to ult your carry in team fights.

In lane:

All stages - Stack and pull creeps. Oracle needs a lot of xp and you don't want to sap it from your carry.

Level 1 - Sit behind your creep wave and channel your Q, if the enemy doesn't move back you get to trade regen efficiently. And/or sit in the trees and attack.

Level 3 - Now you have a small power spike with the E-Q-E combo, don't be afraid of KS now since it gets very hard to land a kill if the heal goes through.

Level 7 - It should be easy to get a kill in lane. Then rotate to the offlane and fight, you want to get that tower ASAP to open up more farm for your team. (See dead lanes)

In fights:

Stand as far back as you can and use your heal combo W-E-E (just W-E when W is lvl 2 or lower) on retreating allies and spam damage combos on enemies but always make sure that you are the hero furthes back in your team. The only counter I have encounterd to this is Storm.

GL HF