Ward placement: Not the brush you see from lane, but the long corner brush right after it. If I feel that they're pretty strong at ganks, then I'll even ward the bush closer to Blue so that it can see when the jungler grabs blue and when he's moving into the river.
For soloing wraiths, it depends on the champ. I tend to start taking wraiths once I can successfully push the lane in good time; if you can't shove quickly when your opponent leaves, then you should be focusing on killing the lane minions (wraiths are worth around 2.5 lane minions, so if you're going to miss more than 2 CS, you should probably leave the wraiths for your jungler (and I prefer to never miss a lane minion).
For Ori specifically (who I'm no pro at), I would imagine that her ranged harass and shielding ability would tend toward not needing health. I could be wrong, though, so check with someone else. If you're mid, you almost always want 21-x-x because mid is the primary AP. If the champ is Blue-dependent (Ori is), then go 21-0-9 for the extra duration.
2xDRings is only good if you're going for early/midgame. However, since most AP mid champs tend to have better midgames than lategames, I see 2xDRings very frequently. I used to main a 4xDRing Cass and my midgame was absurd, but I've since learned that more than 2 Doran's is just a waste for any champ since you don't get the benefits long enough before you end up selling them and wasting the gold. If you're strapped on mana and your jungler can give you Blue often, then I wouldn't see RoA as a bad item; otherwise, just a Chalice should work and then Sorc/Athene's/Rabadon's in any order.