I am trying to set
This is not an ideal spot for cactus and succulents because of the magnolia trees extensive root system and possibly summer shading of the plants below. It would be better to choose different types of plants that are more suited to this environment.
I have a small patch
With a very small garden area, careful planning is essential to maximise your return. It is important to prioritise what veggies you like best fresh from the garden, and cultivate those.