Find a pair of pants and a shirt made from wool or linen that are a little too big. Preferably these will already be brown or gray in color, but dye if needed following the instructions included with the fabric dye. Clothes for the poor in the Elizabethan era would not be fitted, but can include buttons. They would not be adorned with any decorative stitching or other embellishments.
Remove the zipper from the pants if there is a zipper. Sew in buttons to secure the fly of the pants, or sew the opening completely closed if the pants are large enough to get off and on that way.
Cut the hems of the pants and the shirt sleeves to create frayed and worn-looking edges. You can also cut holes in the clothing, and rub the edges with the blade of a pair of scissors to create a more worn appearance. Sew on patches if desired to "mend" the clothing, but ensure the patches are muted in color. Use the rope to secure the pants if they are too big for you.
Scuff the leather boots, and try to wrinkle the leather by getting the boots damp and storing the boots rolled up under your mattress for a few days. Before a performance, wear the boots out on a dusty road or in the dirt. Keep in mind that the boots a poor person would wear in the Elizabethan era would be for work in addition to day-to-day wear.
Accessorize the costume with a worn-looking scarf and a pair of gloves. Cut holes in the items and dye them green or brown, if needed.