Buy and mix together bagged cow manure and mushroom compost available at box stores, enough to cover top of bed about 3 inches. Plant and then spread pine straw mulch. Sandy soils are best enriched from the surface in the south.

Plant in existing soil and mulch afterward. Skip the amendments.

Don't go overboard on the organics, unless you intend to plant anew every year, because you will lose a lot of bulk--as much as half or more-- as the material compacts and subsides. It doesn't retain that nice, fluffy texture.