I would prepare the ground a foot deep, add compost or some other organic matter, and follow instructions as to depth and distance. Don't just dump them in a hole, spread them out. Daffodils are as beautiful as they are indestructible - I won't start without them. But just look at a catalog or a book on bulbs and see what moves you. Maybe it's one of the so-called minor bulbs.
Ornamental onions are glorious, for instance.
Once we put the castle rock all around we were going to raise the bed. We've been told if we add soil around the trees, they might die. The trees range from 4 inches to 2 feet in diameter. We'd probably only need to add 3 inches of soil around the base of the trees, but more like 10 inches around 3 feet out from the trees. They will rot.