I'm looking for a way to build a small retaining wall. I need it to be between 2-3 feet tall and about 30-40 feet long. I'd like to do it as cost effectively as possible. I thought of using pressure treated wood. The retaining wall bricks are too expensive. I thought that perhaps just a simple cinderblock wall would be ok, but it seems a little too hefty for what I need. It doesn't need to look good, as the backside will be facing away from the viewing angle. This is to create a faux mountain side. What do you think the best action plan would be?