I've asked these questions in the past few days, I'll try to answer:
1) Dolls. Eventually you will find a doll stash to put them in. You really don't get bonuses from certain kinds of dolls, I think the bonuses you get depends on the ammount of dolls stored in the stash. I have seen a screen shot of someone that had 1500+ dolls in the stash and I didn't see any bonuses that I would jump up and down for after finding that many dolls.
What I plan on doing is collecting one of each kind of doll and just keep it in my regular stash as a collection. I don't think you can see dolls once you have put them in the doll stash, so I'm keeping my collection outside where I can see it. I will throw my duplicates in the stash though.
Certain dolls can be placed in the cube to create a tome that gives 7.5 million in experience. This can boost a starting character to level 30 in one click. Certain dolls can also be placed in the cube with a rare amulet. Doing this will create an amulet that transforms you into that creature while you wear the amulet. You will be a weakened version of that creature (you can't go hog wild as Diablo) because doing that slows the servers down considerably.
2) The oil can be placed in the cube with a weapon to give the weapon a boost in stats. What each oil does is somewhere in the README. Personally I am saving all the oil for the uber weapons rather than using them all up on the crummy weapons in the beginning of the game. I figure by the time I get a decent weapon in Hell difficulty I'll have 100s of really good oils to use on them to make them that much better.
