There are usually plenty of hangers in the closet and your cabin steward will gladly bring you more if you need them.
I, or I should say my wife, usually packs all the stuff that needs to be hung in a rolling suit bag. She puts them on wire hangers (Sorry Mommy Dearest). The suits and some dresses we will transfer from the wire hangers to the better hangers in the closet. However it makes unpacking and packing easier. You just go from the suit bag to the closet and back.