Okay..... here ya go.
You put up 2" x 6" x 46" stringers at every 48" seam. In the middle of every 4' x 8' you put another stringer, but a 2" x 4" x 46" will suffice. This is provided you use 4' x 8's upright and the stingers are vertical. Cost on that material is about $125. If you use 1/2" MDO, you'll have with labor of prepping and painting another $375 in it. There's your $500 on materials and this includes time for prepping. If you use aluminum composite, the seams might show a little more than with half inch wood.
Do yourself a favor and get a 10' super straight 2" x 4" and use that as a stay for the bottom to hold your panels while you screw them fast.