My advice is to make a list of the plants you want to grow and find out if the conditions they need are suited to your garden. It is a waste of money, time and good plants to try and grow plants in conditions they do not like. To be a gardener, you must know your plants. If you look at the Mediterranean origins of thyme, lavender and sage, you will see that they all like a sunny spot and will grow in quite a sandy, stony soil. As a rule of thumb, silver leaved plants, such as lavender, senecio and dianthus, like to grow in full sunshine and are ideally suited to gardens with a southern or south westerly aspect.
Herbs are also sun-lovers because their aromatic oils are developed through exposure to heat.
Mint is the only herb that can survive happily in the shade. For gardeners restricted by a limited budget, I would recommend plant sharing. Beg cuttings, seeds and plants from friends and neighbours. Keen gardeners are usually quite happy to give away pieces of their plants to friends because they always know where they can get a cutting if their own plant dies. By speaking to other people who are gardeners, you also gain more knowledge.