MucunaPruriens, or Velvet Bean, is a bean that grows from trees and is very itchy to touch due to serotonin on its surface. It is a good source of L-DOPA, and contains some other molecules that may aid the benefits of L-DOPA. The other psychoactives in Mucuna are dosed too low to be relevant.
Supplement-wise, 5g of MucunaPrurients dried powder has been used with efficacy in some human studies on Parkinson's Disease and Fertility. This dose or doses upwards of it should be a good starting point.
If your supplement is standardized for L-DOPA and you are supplementing for an effect attributed to L-DOPA, then start with about 1/2 the L-DOPA equivalent and work up if needed (this is due to the same amount of L-DOPA in Mucuna being more bioactive relative to isolated L-DOPA without carbidopa).
MucunaPruriens can be eaten isolated as a food product, but cooking is required to destroy trypsin inhibitors in the beans (so protein absorption is not hindered) yet cooking also destroys L-DOPA.
Some supplements use the cotyledon of MucunaPruriens, which may have different nutrient profiles relative to the bean or whole root.