A good number of people to start with is six counting yourself. You should have a diverse enough group to have different points of view , but not so different that you can't come to an agreement. Keep in mind not every decision will be made by the collective. Face it, you will not have time to deliberate on every little thing so one person needs to be put in a position that allows them to make the quick decisons needed to keep the assemblage safe.
Whether you are in your compound or on the move, your congregation should be chosen wisely. If you do not already know who your company is you should start looking now. I have told you the skill sets you are going to need in a previous post ("A Few Things You Need to Know"), but did not mention that you really need to screen them. I am not saying that you should have a questionnaire or application to weed out evolutions mistakes, but it's not a bad idea. Your battery should be balanced and complement each other. At first I had no intention of making a questionnaire but the more I think about it I believe I am going to write one now.