These pictures are all fresh wreaths that I made from scratch... but they start out just as boring as plain wreaths at the store- adding the decorations is the most fun part!
When adding Christmas tree balls, I find it best to wire them together and them wire them to the wreath. If they need a little extra support to keep them in the position you want, dab a little hot glue on them in an inconspicuous place. I always use hot glue with pine cones-- be generous- they need to be secure, but if you keep the glue on the back, no one will see it. This won't hurt or discolor the evergreens around it. For a bow, you can buy a pre-tied one or make it yourself. It works best to wire it around the full thickness of the wreath- but be sure to tuck the ends of the wire back into the greens so it doesn't scratch your door or wall.
Keep in mind, if you put decorations at the top center of your wreath, remember to leave enough room for a door hook to come up underneath it without breaking or squishing your decorations. Otherwise, you'll have to hang it crooked.
Happy decorating, and Merry Christmas!