I think accurate observation and drawing should probably be the first thing to learn. This is what sets you up to learn everything else. If you can observe the contour and form of an object as well as draw it accurately, learning things like anatomy, light or perspective becomes much much easier.
This is something we learn at ateliers. We start off by doing Bargue Drawings to learn how to accurately observe shapes and then draw them. After this, we tend to do cast drawings were we study how to communicate 3D objects on a 2D surface with line and value. All of this is done along side daily figure drawings.
Some people often suggest learning perspective or anatomy first. I understand why (this is what I started with) but when someone doesn't have a strong ability to observe and draw what is observed, studying other subjects is hampered by an inability to draw what they intend to.
If a complete beginner came up to me and told me they were serious about learning how to draw/paint. I'd hand them a book called The Practice and Science of Drawing by Harold Speed. The book is about 100 years old but is still one of the absolutely best books on the subject of drawing.