Making your own "glue" aka Royal Icing is easy if you have meringue powder. It's an initial investment of $6-$7 but it will last you a very long time as you don't use much to make a whole batch of icing (and you don't have to fiddle with egg whites). Royal icing is just egg whites, confectioner's sugar, water, and (optional) vanilla. I like to make my own because then you can control how thick it is.
My other tip isn't related directly to the houses. See the green polka-dot tablecloth? It's actually wrapping paper. If you have a square or rectangular table, wrapping paper over a plastic tablecloth (just in case of spills, we kept the same plastic one all season long) is a great way to decorate the table. We used it when we had people over to decorate cookies and it was great because the kids could make a mess and it was easy to clean up at the end of the party. It's cheap, too, if you buy your paper on sale after Christmas or at the dollar store.