I have a few inputs.
Keep in mind that even if you do have plants that are considered low water/zero water/drought tolerant there is an establishment period and they will need water until properly established. I lived in CA for many years and we typically installed plants towards the end of the "rainy season" if there was one. IF you have an irrigation system, that's a plus, but I'm assuming you don't because you mentioned it's all gravel. Plus, that's an extra cost to you with maintenance and water bill.
Also, when picking plants, make sure to pay attention to the mature plant size. The last thing you want to have to do is get on a trimming schedule. Avoid adding spreading groundcovers and plants with indeterminate growth patterns such as bougainvillea.
Should you need a plant list for your area, check this resource: http://www.amwua.org/plants
A few plants that I personally like...
Salvia leucantha has pretty purple flowers and will fill a space
Euphorbia rigida adds a nice blue pop
Rosmarinus officinalis has solid green color year round and does great in full sun once established (keep out of shade)
Muhlenbergia capilaris is a great grass that adds color as well. it dies back in winter though, as do all grasses
Salvia clevelandii is another good candidate that will attract birds and hummingbirds
Then pick out some "specimen" plants to add interest.
Make sure to blend compost into the planting pits to add a degree of water holding capacity and nutrients.
Bam, done.
