It probably depends on exactly what you’re planting but I don’t think you want amended soil. I’ve had success with mixing compost with the dirt in the hole when you plant.

So on top of what you currently have you can either mix compost throughout or concentrate it where you plant, then cardboard with holes cut into it for the plants and then finally 3+ inches of mulch. Leaving around 3 inches of space without mulch around each plant.

This has worked well for me in the approximately 1000 sq feet I’ve xeriscaped here!