I have dyed my own fabrics with natural things found in my own garden, onion skins, leaves, Walnut skins (the best) Gumnuts or bark etc. Great fun, a bit smelly in the kitchen, I usually work in small batches and I set with salt vinegar and soda or mordants bought from a craft supply shop. Then heat set. It is always a bit hit and miss but that is what I like about it! Natural dying costs nothing basically and the colours are never really bright always soft and subtle, as long as you are prepared for that, however if you keep over dying you can intensify the colour. My colours are always from nature/natural things.
Gal