Years ago I used an old wooden milk crate that was heavily lined with newspaper (bottom and sides) and filled with compost and topsoil. I kept the box in a cool, shaded area with an old window screen for the lid. This simple set up served me well and had I not gotten into fly fishing I would still be using it today.
I traded a spinning rod set up with some worms, shot, swivel and #8/10/12 size Eagle Claw hooks for pricey rods, reels and thousands of $ in fly tying equipment/materials. I wonder if the trout appreciate my efforts or even care. LOL