What is the most basic material for photography?

See what your future shooting direction is. If it's a portrait, I suggest you take a plaster statue first. In a year or so, you will know the structure of people very thoroughly. If it is an advertisement, I suggest taking some plaster models, such as cylinders, cones, triangles, circles, cuboids, cubes and so on. If it's scenery, it doesn't matter. If it is news, it is natural.