I turned some shitty clay into a nice garden by adding lots of dried leaves as a mulch and then just letting the worms do their thing (I never mixed them into the soil, just watered them).
As for attracting pollinators I'd go with chives, sage, and borage. The chives bloom in the early spring and the bee's go nuts for them. Shortly after that that the sage will bloom, and then following that the borage will produce flowers for a good two months at least. Chives and culinary green sage are perennials, so once you get them going you're good to go. Borage tends to reseed itself in the same area. I usually mulch heavy-ish around the borage with grass clippings and then the following spring the new plants are pushing up through the old mulch. Chives make tons of seeds that tend to spread, and sage just becomes a nice large bush, also great tasting in your stuffing if you dry a bundle or two in the fall. The borage flower are edible, and make nice garnishes for whatever, if you're into that girly stuff.
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(from left to right - chive flower, sage flower, and borage flower)