You can do it and grow a garden no matter what type of soil you have! Lots of herbs and veggies grow great in containers and a five gallon paint bucket with drainage holes drilled in the bottom is large enough to grow tomatoes, cucumbers, and zucchin, one plant per pot. You can also recycle 5 gallon black plastic nursery pots for container gardening. Succulents grow well in potting soil especially in shallow clay pots as succulents do not have deep roots. Herbs may be able to grow in your mostly gravel soil as thyme, oregano, rosemary and other  Mediterranean  herbs actually prefer a quick draining gravel soil. Lavender also prefers a dry soil with really good drainage. You can make mounds in your landscape using topsoil that sits on top of your gravel soil if you want to grow crops like beans, peas and flowers or build raised beds and fill them with good soil to start your garden. Welcome to gardening and Keep Growing, Marianne Binetti