For inexpensive "raised bed" planters, you can use storage totes. I drilled a few small holes in the bottom for drainage. For most things you'll only need about 5-6" of soil, for which I use potting soil. My native soil is clay - I'm working on improving it to plant more in the ground in coming years. So, to fill them up I put some pine cones in the bottom 4-5" or so, since I have a large pine tree that drops more than enough. Then I add a few inches of last year's grass clippings on top of that and leave about 6" for soil. Shake it up a little before you think you're done, because those bottom layers will settle over time anyway. I can get 2 tomato plants and a small pepper plant in one of the 18 quart totes. This year I'm going to try adding some carrots to grow in between them and put peppers in their own planter.