I used to make these when my kids were little, and all I used were frosted ginger cookies that came in small square shapes. I just hot glued everything to a box shape I had preplanned, and added all the decorations from leftover candy from Halloween.
One thing I can think of is that you can buy candy that looks like rocks and use it for a walk-way to the house. I think I used frosted mini wheats for the roofs of my houses, and I also used peppermint candy canes outside the houses for lamp posts. Another thing that would be cute for a house is that red, white and green "reindeer corn" I"ve seen. I used those licorice strips to frame out windows (the red ones--dont' know the name of them).
This year I'm doing something similar. I found at the Wonder Bread store packages of pink-iced gingerbread planks in a box for $3. I think there are 12 planks in the box, so that should be enough for a house. My Wonder Bread store sells bread at a discounted price and also the other Wonder Bread products, so there might be one in your area.
CVS has their candy for 88 cents a bag, and you should be able to find some things to use for decorations.
Have fun and good luck!