I'm similar in my approach, Jo Ann. Do often start with a rough idea of the basics, like bed shape, type of foundation plants, clay soil tolerance, and drought tolerance (especially necessary here!). But it mostly just develops as I go, and from the lesson-learned fallout of my abysmal ignorance in the beginning. Now, I see something I really like, check to see if I can grow it, start looking for similar and/or complementary colors, shapes, and/or textures--and those on sale
, and it snowballs into a purple and red daylily plot; a grasses, Iris, and sedum curbside bed; or a roses, Dianthus, and clematis decorative fence line. Still have a LOT of work to do to get the Green Amber side yard cleared. Just haven't figured out how to get rid of all that nasty weedy grass stuff without a lot of back breaking labor that I can't expend, or harsh chemicals that I don't want to use. At least I do have most of the Iris and Daffodils dug out and moved, so that will make it easier. But even here, it will be mostly serendipity as to what structure and contents will be put in.