#1
what strings can i put on an Ovation Celebrity? are .010 OK or will it be better if i put .011?
#2
at least 11s....i wouldn't go any lower then that on an acoustic guitar. I prefer 12s or 13s myself. (be careful with 13s though...there is a lot of extra tension).

PS

12s probably came on the guitar.

Gear:
Partscaster/Tele into a bunch of pedals, a Maz 18 head, and a Z Best cab.
#3
.12s would do a find job. Try Elixer nanoweb, but they are exspensive.
My Gear-
Schecter 006 BlackJack
Ovation Tangent T357
Fender Hot Rod Deluxe
Roland Cube 60
Boss NS-2, CE-5, DS-1
DiMarzio Pedal Couplers