Garden landscaping: when do you start planning?

I can lay out the garden myself. We also planted everything ourselves and sowed and grew the lawn. What is difficult at least for me is the transformation of the construction wasteland into garden-ready land and the creation of paths and terraces. Specifically, topsoil had to be brought in and spread, which was a breeze with the help of a company and their machines. Drainage had to be installed, leveled, and paved, as well as a slope supported and a staircase built. I also outsourced this. K.