Raised garden beds can be purchased at most home improvement stores, but you can build one for less than buying one. With a little creativity and desire, look around for materials that you can use to create walls for the garden bed. Once you have something that can support the soil, you're in business. Cheap raised beds can be uninstalled at the end of the growing season or left up for next year's garden.
Make a box out of straw bales and fill the center with soil. Soak the soil and the straw bales before planting. The straw will slowly decompose into the soil. At the end of the growing season, mix the decomposed straw into the soil and let it compost for next year. Place new straw bales around the soil each year. You can purchase straw bales at your local farm supply feed store. Get the bales with three strands. These are stronger and last longer.
Arrange rocks in a square, circle, triangle or whatever shape you want. Make the bottom layers of rocks wide enough to support the rocks you place on top of them. Build the wall with pyramid layering so it won't topple over. Fill the inside area with soil and plant your garden vegetables or flowers. Keep the walls no more than 4 feet apart. This will make it easier for you to plant, cultivate and harvest the garden.
Bricks or Blocks
Butt blocks or bricks end-to-end and form a square or rectangle raised garden bed. If you use cinder blocks, set the holes in the blocks vertically and fill them with soil. Plant strawberries in each of the holes. Fill the inside area with soil and plant a garden. You can use mortar to connect the blocks or bricks, but it's usually unnecessary. The bricks and blocks will absorb heat from the sun during the day to keep the plants warmer longer.
Plastic Swimming Pools
Lay down a few inches of gravel on the ground. Poke holes in the bottom of a plastic swimming pool designed for small children. Fill the pool with soil and plant your garden. The gravel beneath the pool will allow the water to drain out and keep the root systems from rotting. Use as many pools as you'd like and plant a different vegetable in each pool. Fill the soil to the top to ensure the plants get plenty of depth for their growing roots.