Sand is very free draining, clay is not although it is usually full of nutrients locked in tight in the structure.
By adding plenty of well roted compost, leafmould or manure (over a year old) this will add organic matter which will help break down your soil structure and make nutrients available to the plants.
It also looks like you are on quite a slope.
Sun/ shade what do you get?
Think about what plants do well.
Climbers up the fence, plenty of choice for all aspects. Woodland plants for shade such as foxgloves, Hostas and ferns.
If you have plenty of sun, then think Delphiniums, rubeckias, daisies such as shasta. Also think of the height of the plants when fully grown, when positioning.
Some shrubs will grow well in both conditions and hold the soil in place to stop the soil slipping.
Maybe some well placed logs or rocks. A
Hope this helps. Please look at some of my pics as I have a slight slope.

Wow ditto great advise Treesandthui said it all

Thanks TST and great