The Meditations is indeed a great work but it is also one that I would not recommend as the first reading in Stoicism. It is very challenging in a translation that tries to convey the meaning closely to the original language. It was written in somewhat complex Greek style and meant as a personal study instead of addressing a wider audience. For instance, the Moral Letters by Seneca is a far more palatable way to get up to speed on Stoic thinking.
It is also worth your while to get acquainted with Stoic thought and concepts before studying the classical works and especially the Meditations. Nature is one of the key concepts of Stoic philosophy and nature or natural there does not imply the many things that we in this time and age may understand. Stoics believe that all thought should be in accordance with nature, and that nature is more like the laws of physical nature.
For instance, if it is the way of the nature that all living things eventually die, a person should not wish to live forever or think that it is unfair, but accept that as the way the world work and consciously work towards adjusting his behavior and expectations to the realities of the world we live in. Stoics believe that aspirations that are contrary to nature are irrational and thus unvirtuous (immoral). They cause us to suffer and skew our rational thought. And often set us on unvirtuous courses of action.