Hi,
My yard it solid clay 10cm in, I was adviced to add gypsum to the soil as I have added quite a few garden beds, its helps drainage, though clay apparently has some nutrients is is very poor on drainage. I am definately no educated gardener but am learning as I go along, I figure it depends on the soil you have as to the benefits and what you are planning on planting, but if like me you have a clay based soil it will allow the roots to grow and spread as they need to, as in my place plants tended to get water logges and die, adding compost etc will aide in plnat growth and health, sorry other than that Im unsure what gypsum isactually bebeficial for.
Happy gardening

Used to break down clay soil, but not advisable to use on planted ground, best use is on newly dug fallow ground.

many thanks