You might want to do a jar test on your soil since it is hard for you to judge the texture accurately without a lot of experience. And even harder for me!

In your semi-arid climate, equal parts of sand and any kind of grit or gravel (except limestone) should work. If you plan to grow temperamental species that might rot then forget the sand and just use gravel. Decomposed shale might be available in your area. You might want to call a builder's merchant since you'll be wanting a ton or two, I imagine?

I would avoid the bark. Since I of course don't live in Southern California, you might want to wait until someone local comments. For many succulents, Yuccas, Agaves, even some of the big cacti, your native soil with a nice top dressing would probably work.

Thank you shrubs n bulbs. As to the native soil, unfortunately the natural land here was stripped away and ruined when the area was developed, and what was left as topsoil is onerous, valueless, unworkable stuff- selling at about the highest per square foot price in the country.

To anyone: It also occurs to me- is there any reason I shouldn't just acquire the large bags of "Cactus & Palm Mix" available at Home Depot and use that in a raised bed?

Avoid the pre-made mixes, they contain lots of peat which won't help garden soil much in the long-run, and the perlite can float to the top and look annoying.

Lowe's carries "pea gravel" which can be added to aerate the soil. Other than that, you should be fine with your average garden soil, unless the pH is extreme. The plain bags of topsoil sold at Home Depot or Lowe's can be added to increase the soil volume.

Avoid the bark and the pre-packaged soil mixes. The soil mixes are best for containers and even then you need to alter it with some other material.

I suggest trying to find a landscape materials yard that sells bulk quantities of decomposed granite (and other stuff). Here in AZ they are all over the place. Ive had great success mixing in some 1/4" minus granite with my native soil for raised succulent beds. 1/4 minus has enough gritty and finer particles to provide good drainage. You can have a few tons of this delivered to you much cheaper than anything you can get at HD or Lowes. You can also get a nice top-dressing material fron them.

If you cant find one in the phone book, maybe call up some landscaping contractors and ask them where they get their non-plant materials. Good luck!