Here I list plants that are worth your time and money, I have personal experience with these plants and have been growing them for at least two season or my close friends have:
Rudbeckia fulgida Goldsturm, Black Eyed Susan.
These flowers do best in my garden in full sun. They do not require a lot of water but if the soil is poor (hard clay) they might take a while to get settled. They reseed well and will fill up nicely very quickly. Their seeds are the delight of Finches. Long lived flowers. good fall interest.
Brunnera Jack Frost
This plant is incredible, you can divide it at will and the next year you will enjoy full plants. The spring flowers are a wonderful blue and when passed the leaves take over the show for months to come. They are much easier to grow than Hostas. Plant single or en masse. Makes a great underplanting for peonies. These photos were taken less than two months apart.