Maybe I'm cheap, but it always hurts buying Christmas wreaths every year. It's so easy to drop $40-50 just to buy two wreaths for the front and back doors, only to throw them out not long after New Year's. Starting last year I got tired of throwing that money away and decided to make my own super-simple swag for our doors.
We're lucky enough to have a lot of hemlock trees behind our house, so I took some clippers and headed out to trim back some branches that needed to be cut anyways. Our dog followed me out to "help" - and by help I mean run around with a branch I cut. If you don't have suitable trees in your yard you may be able to get away with using the trimmings off your Christmas tree or you can buy bundles of hemlock or fir tree at the grocery or craft store for pretty cheap.
I made some smaller cuttings and started fanning them out, making a rough diamond shape.
Once it was getting close to what I wanted, I used some hand clippers to trim long pieces back into shape. If you have holly or other greenery you want to add, now would be when to do it.
Once I was pretty happy with it, I used some craft wire to bundle it together. You want to make it pretty tight so none of your branches slide out over time as you open and close the door. Use some extra wire to make a loop at the back for hanging.
Now add your bow. I had our bows made at the local garden center a few years ago. They had spools and spools of different fabric ribbon available, I picked the pattern I wanted and they made me up a couple of matching bows. I think they cost me $7 each, but I reuse them every year so it was definitely worth it! These bows have some wire in the back to attach it to the swag. After you add the bow, do any final trimming of the greenery.
This finished swag cost me nothing this year since I already had all the materials, and that's just fine by me ;)