People say you should not use chicken wire. It is not safe at all. Most people that use it end up crying with all their chickens killed. You should look for welded wire instead otherwise you will lose all your chickens to dogs, racoons, etc that can just break in chicken wire very easily.
That 50 feet should make a 12 foot x 12 foot pen that is 4 feet tall. You can get 50 feet of 5 feet tall for about $47.00. Then you could get a bird net to go over top but only if they will be locked safely inside a secure coop at night. Otherwise buy some more welded wire to roof it. Best to have the coop inside the pen so it is two layers of defense.
I think a sticky with some of this info would be good so people can find it easily don't you think?