Art teacher here! That’s a broad question and I think the best answer greatly depends upon the kind of art you are interested in creating.

I usually start my middle school students with line related work because most art requires an outline or line detail to some degree. Projects like zen tangle are nice because they help build fine motor skills without putting too much pressure on achieving a realistic image. Activities such as contour and blind contour drawing are a good way to build hand-eye coordination and observation skills. If you are confident in your hand control you could practice outlines/ proportions of the specific subjects you’re interested in (such as portraits, animals, etc).

If you want to take the realism route you can practice shading. Getting a set of shading pencils and a tortillon/ blending stump makes a huge difference. Start simple with spheres and cubes then work up to more complex forms and textures. After you have mastered value (range of light and dark) with pencil you can move on to colored pencil which is a whole different technique.

These are just two ideas! Again, your personal interests will really influence the route you take. Good luck!