At least ten.

We need to now what the room is being used for before we can give an adequate answer.

This is particularly true in determining the number of circuits you will need for the room.

Also the type of lights you will be using are important. For example if you want to use a High Intensity Luminarie versus a 60 Watt incandesant bulb.

As Don mentions, need to know the purpose of the room and type of fixtures, along with ceiling height, types and colors of walls, ceilings, and floors.