If you have a limestone based road base as is typical in central tx then grade it first if you are indeed adding gravel to the top. The term gravel means rock of particular size or sizes. Road base will include fines and will need to have a plasticity index of between 2 and I think it's 7. A proper road is built with a base material of graded material of the proper blend of sizes and the proper clay content to achieve a plasticity index that will hold together and compact while still having enough angular aggregate to hold it's shape. Gravel is used on top of the prepared base to provide a smooth surface that is easily regraded. In central Texas, unpaved roads are usually constructed of only the road base portion as we have limited access to proper gravel unless you have it hauled from the granite sources out west near fredericksburg. What we use for base to build roads is 1 1/2" to dust. The larger rock is required to help hold it's shape and minimize the formation of potholes. If the slope of the road is not too great we will use 3/4" to dust to top dress the road. Moisture content at the time of grading is critical. There is much that I am leaving out as it is not a simple subject and the correct approach varies by topography, season, moisture, drainage, sub-grade and available materials.
Without knowing exactly what your conditions are, I would say grade first. Also, proper crown is critical to durability. The steeper the road, the greater the crown that is required. If your slope is greater than 7%, it should not be unpaved. I wish they had followed that rule when they built the subdivision roads that I maintain.
