Most people seem to use mostly shavings or leaves for the dlm... and don't forget some sort of lime or PDZ. I was looking for free options, and wood chips are often available for free, as are leaves in the fall. Wood chips or even shavings do take quite a while to decompose so you do need the...
To use in a run you might want to see if you can get wood chips or mulch from the city or your neighbors when they trim trees / shrubs or pick up the leaves in the fall. Around here I see some cities periodically advertise that you can pick it up for free or small fee at the dump etc.