Do gear of Oriana arrive ready when animated?

Yes — a gear that Orianna animates comes out ready, so it can move and attack the turn it becomes a unit.

It never "arrives": Lady of Clockwork just changes an object that's already on the board into a unit gear, so there's no new entry and nothing to set its state. Gear enter play ready (Rule 149.1) and only exhaust via an activated cost, so in practice it's already ready when you animate it at the start of your Main Phase — and importantly it does not pick up the exhausted entry a freshly played unit gets (Rule 359.2.c).

The exception is if the gear was already exhausted when you animated it (e.g. you'd tapped it for a [T] ability that turn) — animation doesn't ready it, so it stays exhausted until your next Awakening Phase.