What is the best way to build a raised garden without using wood?

container gardening in 5 gallon buckets with holes in the bottom works greaT.

bricks, go on freecycle, online. perhaps someone has some to give away.

Bricks for border.

Trex, a non-wood deck product would most likely work if you needed a garden box that's tall. I believe it's made of vinyl. My raised beds are made of stacked concrete blocks, three layers tall.

My friend gardens in metal horse troughs and they have lasted for years. Just drill drainage holes.

Galvanized tubs, cinder blocks, 5 gallon plastic containers, plastic bags that held rice or petfood. Hobby stores have pretty bags. You could use the store bags that are sturdy, many grocery stores sell them-the reusable ones people bring in to carry their groceries home.

Just be sure they have drainage.