Look for inexpensive wreaths at Goodwill type stores. You can add your own touches to them to make them look better. Use pinecones around your displays. Leave them plain, or spray the ends white or glue cotton on them. When you make a display, remember to vary the height to make it interesting.
Candles give height and always look good.
Use ribbon to add texture and interest. It is better to have one nice display than several which look sparse. One idea to add drama at night to a display is to use lights. Cut out a Christmas shape or use a picture, and then light it from behind. You can do this indoors in a dark corner, or on a larger scale outside.