I found this year that using a moisture retaining potting soil had its pros and cons. I didn't have to water nearly as much, but the herbs on the porch railing didn't grow as much I as would expect. The flavors were more intense, at least with the parsley. So, I'll be sticking with regular potting soil next year or the kind with slow release fertilizer.
You can do gardens in a myriad of containers from old boots to washtubs to ceramic urns - anything that will hold soil and plants. One thing I will try next year is stumps. We have a couple of old stumps that will get hollowed out and plopped in the garden for a very natural look. I don't count on the plants making it over the winter, but I might try hosta just to see how it does.
Perfect for the shade garden!
A Victorian planter in Riverside
What to do with Aunt Maud's old Chinese planters.