The cheapest retaining wall to build is usually a simple, earth-filled mound. You can also use recycled materials such as old tires, plastic bottles, or bricks. If you are looking for a more aesthetically pleasing option, you can use wooden boards or stones to create a retaining wall. However, these options will be more expensive than an earth-filled mound.

The cheapest retaining wall to build is usually a simple, earth-filled mound. You can also use recycled materials such as old tires, plastic bottles, or bricks. If you are looking for a more aesthetically pleasing option, you can use wooden boards or stones to create a retaining wall. However, these options will be more expensive than an earth-filled mound.