It's really easy, once you know how.
Lavender thrives in the Mediterranean. It loves to be hot and DRY. It prefers to grow in sand or gravel and will often self-seed onto a gravel pathway and thrive there, whilst sulking in the flower bed which has nutritious soil.
My plants always used to die after a couple of years and I always wondered why. When I learned what it likes, I planted mine close to the house in builder's sand and it has been happy there for years!
Munstead is a good, hardy variety that has done well for me, Hidcote is another. Some are not hardy for me in zone 5B, so hardiness is always something to consider when choosing a variety.