I was recently told by an experianced smith at a recent IBA meeting that a new smith needs to learn consistency. They must first master the beginner skills. They have to learn to maintain a good fire and not to waste fuel. They need to learn hammer control. If you have no idea WHAT metal you are interacting with, it makes learning how to work that metal very difficult.
He suggested buying mild steel stock, so you are working with a consistent size and type. For example some re-bar is low quality "junk" steel, and will only frustrate a learning smith, and inhibit learning.
Oh and experienced smiths have trouble with wrought iron sometimes due to the fibrous nature of the material. I would personally avoid this if you are just starting out.