A difficult situation, but take heart. Go to the bottom of the page and click on S and you will find a list of plants for sandy shade.

When you plant whatever you decide upon, make a planting pocket for each one. Dig out a space and incorporate slow release fertilizer granules and water retaining gel crystals into the soil at the bottom and at the sides. Add compost if you have some or if you're trying to plant into JUST sand/ gravel. When you put the plant into the hole arrange it so that there is a "watering platform" behind the plant - a flat area that allows any rain or water that you supply to soak in close to the plant and not run off down the hill.

I have similar conditions to yours, with added rocks, so when I make a hole I get several rocks out every time. I arrange these at the front like a balcony to enlarge the flat space available to put the plant into and to help slow down water / rain as it goes down the hill.

Another tip is - don't strip off all the existing vegetation (assuming there is any) at once, as its roots are holding the whole heap or hillside in position.

Clear a space round the plants you're putting in now & be prepared to take out more of the unwanted lot & add more wanted plants later, after the first batch of planting is established.
I hope this helps.

How large is this area? That will make a difference to what will look good in it. Try ivies to trail along or Vinca, major or minor. And maybe some ferns such as Dryopteris or Polystichum setiferum.