There are two constant challenges I come across growing im my arid gardens. The opressive full sun and almost no water.
Mechanical and chemical ways to negate this abound but just planting things that actually thrive in this environment is alot less effort. Its the cheapest and typically leads to more bountiful harvests than the other two options.
Sunflowers are where we'll start, they are ornamental, edible, effective self sowers, cold hardy and fill a space thats typically very hard to fill in dry gardens.
Moving from the back to the middle, I like to fill in this area with Delphinium ( Rocket Larkspur) or Echinacea. Both can thrive on similar neglect and sun so mixing them together can add some interesting contrast in texture. Though I tend to plant more Echinacea, its a nice herbal tea.
Up front my favorite are marigolds, great at repelling all sorts of pests and very low maintenance. Marigolds are a great place to start for a budding seed saver. Brocade is my favorite variety and I have found it to be the most drought tolerant.
Depending on your season and climate you can get away with skipping water day for months when you do an arrangement similar to this. Ditch the drip tape and shade clothe and just pick up some simple flower seeds!