Plant ideas for poorly functioning wicking beds

So,
To set up the scene I am newly in charge of a long neglected community garden in Central Tx, zone 8b with around 38in or rain per year with hot humid summers and cool mild winters. All of the beds in the garden I inherited are wicking beds that had been filled with commercial potting soil many years ago. After many years of neglect the soil in all the beds have settled by 6-8 inches into the gravel underneath, which leaves the surface of the soil just barely above the drain level (and the drains are clogged with grass). Digging out all the beds or even a few of them simply isn't an option due to time, labor, and financial constraints.
The only answer I've been able to come up with is to build the soil level back up to give myself some growing room above the anaerobic zone and monitor closely how much the beds are watered. What I have available to me is: the native soil which is derived from a thick red clay, the compost pile of reject plants and potting soil from a nearby commercial greenhouse, and an ongoing supply of composted horse manure.
My main question here is what would you, my permie friends, try to grow in these beds with these conditions?  I will be in charge of this community garden's planting and fertility regimen for the foreseeable future so anything that grows is a possibility.
Thanks!

Hi Jass, welcome to permies!  I'd be quite tempted by both the composted nursery pile and the horse manure.  BUT, I'd test both first to see if there are persistent herbicides in them.  That can be done (so I hear) by getting some of the material to be tested and growing some bean seeds in them.  Within 10 days, if they don't look like healthy bean plants, I wouldn't use the material.   Maybe do a control set of bean is your existing soil.  If you think the material is too rich to use 100% for the test, dilute it with some normal soil or potting soil before planting the sacrificial beans.

As a bit of further context the only things that were intentionally planted that survived the neglect were asparagus and mint, both of which are doing stunningly under their neglect regimen.

Well, what will grow well in thick red clay?

In my experience the following would do great:
Wood sorrell, curly dock, day lillies, lambs quarters, wild carrot, yarrow, broaf leaf plantain, thistle, dandelion

Ie, wild edibles will do great.

If the clay isn't too densely packed you could try sweet potatoes or sunchokes.  Both are good for soil building.  Both are also edible.  Beans and Peas can also tolerate clay though they'd be a winter crop for 8b but you can drop them at the end of the season for more mulch.  For another long term producer with massive roots you might also look into Rhubarb.  I think it does ok in the heat and would help to break up the clay.  You might also look into a service like chipdrop or something similar in your area.  Or just talk to some of the companies that drop trees.  Free mulch would be very helpful.

I would avoid adding any clay soil, if possible.
The potted plant soil is ideal for a wicking bed.
I would try to find some fiberglass window screen as a barrier between the existing soil/ reservoir and the new soil/ plants.
I would plant things that most need a consistent water supply to flourish.
Tomatoes do great in my wicking containers.
If the horse poop turns out to be tainted , plant peas  and eat the foliage.
The only plants I have had that didn't like a wicking container were the herbs, they seem to prefer some dry root time.

I feel I was a little unclear in my previous post. I'm not trying to plant anything into the native soil, I was just describing a bit of it's characteristics for context. At most I would be taking a small amount of local topsoil from the nearby pastures or woods to introduce some of the native soil biota. I have a feeling tomatoes would do well and I appreciate the suggestion. I've also got watermelons and cantaloupes that will hopefully be thirsty enough to keep the top of the beds stay a bit drier. We shall see though!

I'd work into the existing soil, new amendments like compost, sand and wood chips these will help recondition the existing soil and increase the available biology.

You do need to think seriously about having some work weekends with others and reconstruct one bed or even half a bed at a time, that will really go a long way at achieving your goals.

As far as plants go, squashes (both summer and winter), cucumbers, tomatoes, and every other water hungry plant you desire to grow will do very well.

Redhawk