If ever there was a truism, this is the truism of all truisms. I have gardened on a variety of soils including soot, gravel, clay, sand and loam. Without a doubt, loam is the best for high production tasty vegetable and fruit. The question is, can you make soot, gravel, clay & sand more like loam and can you make loam better? The answer is undoubtedly YES and the METHOD is ADD COMPOST.
Sometimes you may be able to get well rotted horse manure from a nearby stable. I was once lucky enough to get ten cubic yards of four plus year old horse dung and rotted straw. It was as black as the Ace of Spades and very crumbly. I dug it all into a cleared sandy border which I then planted up. The plants absolutely bombed away. Unfortunately I did not keep up the treatment and each year the plants became weaker as the goodness was leached away.
You can become independent of luck and good fortune and make your own compost. You can then regularly add your own top up to your soil, whatever type it is.
The first source of compost material is your own garden. Grass cuttings, annual weeds, prunings, autumn leaves can all be collected & recycled. Pernicious weeds...