I recently started with dying wool, I used a load of onion skins that I had collected over a few weeks. I mordanted the wool using Alum, then dyed using the onion skins. I got a beautiful golden orange. As an experiment I added some rusty water to the dye pot and then returned a second skein to the pot, this took the orange down to a golden brown.
Very rewarding exercise. There is lots of info out there on how to dye wool, and onion skins are available for free.
J