It's worth having a soil test done. I have very sandy soil and the soil is extremely low in nutrients--Nitrogen, Phosphate and minerals. For the first three years, many plants I had moved in from four miles up the road either died, just barely hung on, or refused to bloom. I've poured on a fortune in organic supplements--rock phosphate, organic material (esp. leaves), commercial compost, Planters II--a mineral supplement, and nitrogen in the form of dried blood.

Sandy soils drain very fast, and so nutrients wash out of them. After a rainy summer, a couple of my shrubs so signs of nitrogen deficiency, even though I give them a good boost of the dried blood every spring when they leaf out.

A handsome shrub for shade is Eleutherococcus sieboldianus 'Variegatus'. Not sure if it's hardy to your zone, but the green and white variegated leaves are very handsome, though the flowers are insignificent.