Sandy Soil

[Gardeneer]

Recently I moved to NC, its most southern tip in Columbus county, very close to SC.
According to one soil survey the native soil is 93% sand. But what is SAND ? Broken pieces of some rocks. So is the CLAY !! But apparently it takes longer time for the sand to become fine power but it happens or can happen !
So they describe some sandy soils "Sandy Loam".
In my case it is quite sandy. I did a quick test. It turned out about 20% humus and the res SAND and LOAM.
What is the remedy ? I have made about 500 sq-ft garden . Cannot afford to buy bagged stuff, there is no place nearby to sell bulk compost.
WHAT I AM DOING :
1) raked /collected as much fall leaves I could, about 10 loads of tarp.
2) raked /collected as much pine needle I could, about the same as leaves.
3) there was a big pile of wood ash accumulated over the years by the previous owners, about 16 wheelbarrow loads of ( 5 cu-ft each = 3 cu-yrd), mixed with some humus.
After turning and removing Bermuda grass roots, I layered leaves, pine needles and spread the ash/humus on top and let it over winter. Come spring, I will till the whole thing. Hopefully by the the leaves and the pine straw are broken down.
In the meantime I am looking to find stuff like cotton seed meal, alfalfa ... compost.
I will have to optimize my resource and will further amend each planting hole with fancy and more costly material like peat moss.

It is not over and I am not done yet. That is why I am here seeking advice