Often our attention is drawn to the size of an article within a dream. Gravel in this context is simply an indication of small particles. Such a dream may also bring back memories of a particular time or place, and remind us of happier times, such as those of childhood.
Skidding on gravel signifies that we should avoid taking risks in everyday life.
Gravel in a dream represents obstacles, and if you walked on it, you will have to expend some effort to overcome the difficulties; but if you drove over it, the problem will be quickly solved.
If you were spreading the gravel, your dream was telling you that the trouble is of your own making and you would be wise to reconsider your attitudes.... The Complete Guide to Interpreting Your Dreams
Maybe you need to get rid of something, or think it is time to have a spiritual washing. Spitting can represent fury and contempt.
Dreaming of spitting predicts the sad ending of what seems to be good business. To look at others spitting predicts disgust and disagreements. The most superstitious people believe that after a dream that predicts bad luck, if you spit three times right after waking up the harbinger will disappear.... The Big Dictionary of Dreams