If you have neutral or alkaline soil, tottenham, alliums are very easy to grow. Just buy the bulbs and put in pot or border, about three times the depth of the bulb. The large purple ones look stunning planted to rise above lavender bushes. They look best in big clumps with something frothy beneath tem as they stand up like soldiers and need softening, I think. Alchemilla mollis would look good or pink hardy geraniums.
To ensure the bulbs go on flowering year after year don't let them seed, but cut the flowerhead down to 2inches when it is past its best. Have a go. I think you'll get gasps of admiration for your display.