Everbody loves lavender, and Lavender "Munstead", the best for the US, is a best-seller every year with our perennials. There's all kinds of detail on growing it on the site; click here for the details. But all you need to know is that lavender is really a desert plant--do not put it into "good garden soil", or it will simply die. Thousands of lavender plants are loved to death every year in the US, since so many gardeners plant them in rich loam, and fertilize and water them to death. Lavender is one of a good sized group of perennials that absolutely insists on quick-draining gritty soil--what most of us call bad soil--rocky, arid, desert-like conditions. I always recommend making a part of your garden your "desert"--bring in some sand, maybe some gravel, and make sure that area is in full, baking sun and has perfect drainage.
Then in that spot, plant your lavender, liatris, yarrows, and other plants that hate the soggy, muddy soil we try to create for poppies, peonies, and all the others. The photos here are of a famous lavender garden in Oregon. The magnificent red flowers through the gate in the midst of the lavender are red crocosmia "Lucifer", a spring bulb we sell and one that makes a dramatic show with lavender as you can see below. Unfortunately, you can't smell this garden on your computer, but trust me, it smells as heavenly as you imagine.