It depends on what kind of free range you want. If you just want your cham to come out for a couple hours WHILE YOU WATCH HIM then just a simple large plant or tree will do. If you want a 24/7 free range then the first think you need to think about is a safe area for your cham. Do you have a room you can set up a free range in where you can close the door and he can't get out and you will need to cham proof the entire room because they do roam from time to time. Second you will need everything in the free range that you have in the cage....same lighting, branches and so forth. I cup feed and hand feed all my animals. If you are new to chameleons I would recommend getting use to doing everything correctly in the cage first and then once you are successful at keeping your cham alive and healthy in a cage then think about a free range.
I have a nice cage for my cham and I let the door stay open, I then have a rope to a decent sized plant (right in front of a window) I use rope because then I can close the door if I so desire without having to move the rope. Also the plant is on a short plant stand, kahldris (my chameleon) isn't going to try to go to the floor he is quite happy going back and forth!