The last hugelbeet I built was dug three feet down, 18 feet long, and
rose three feet from ground level (six feet of height in total).
It contained the corpses of two middling Manitoba Maples, which are invasive in our area, a Christmas tree, and as much more woody debris as I could fit in while maintaining a sufficient soil thickness around the wood. To this I added cow manure, two years accumulated
compost in a range of levels of completion, the topsoil, some mineral soil, and the soil from a 3-foot trench around the bed, which I filled with woodchips after. I mulched the top and sides with three inches of wood chips.
As soon as I was happy with the structure of my hugelbeet, I started planting potatoes. I did most of the whole thing with potatoes, garlic, and horseradish, and I hilled up the potatoes as they grew with more wood chips. Along the north side, where there was a
fence for support, I planted cucumbers, beans, and beets.
The potatoes and horseradish exploded. The garlic did very well. I didn't really get any cukes, though I found lots of chewed ends (I hate squirrels). The beans thrived, and the beets were huge, and I found a butternut squash
volunteer from the compost addition that grew several butternuts longer than my forearm (and they were delicious).
So in my opinion, if you are going heavy on the manures, you are safe to do heavy-feeders like beets or squash, but potatoes can thrive in areas of disturbed soil, even with large clods, in ways that others just don't, which make them particularly well-suited to a new hugelbeet.
I would suggest you start with a potato guild complete with supportive plants that are also crops in themselves(horseradish increases potato disease resistance, peas have been shown to decrease Colorado potato beetle populations, garlic and most other alliums do well to create soil conditions unfavourable for certain types of detrimental soil life, and marigold and thyme both deter pest insects).
Perhaps the next planting could be the three sisters, or some variant thereupon, using squash as living mulch and a nitrogen-fixing bacteria host like beans to
feed it, and some kind of structural crop like corn.
Some more info would get you better advice. Whatever you do, have fun. Keep us posted, and good luck.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein