I prefer to use an extension cord and wrap it up the tree’s trunk. That way, lights can be added starting at the top of the tree versus starting at the bottom.
By “filler” I mean pretty things you add to the tree, similar to something you would find in a floral arrangement. Filler adds interest to the tree and helps fill any holes.
Ribbon adds texture to the tree. There are several ways you can add it. You can wrap it around the tree, you can stream it down the tree starting from the top and you can cut ribbon sections and add sporadically through the tree.