Levelling gravel is a necessary evil for many landscape projects: You've got to level it before you move on, but you may not have the right tools and may not know how to do it. Use objects already in your toolkit to make your own gravel drag. Not only do you save on cash, but you get the level reading you need. Leave yourself adequate time to make the drag and level the gravel, so you're not rushed.
Plan your project's grade first. If you're laying a gravel driveway, you might need a gentle slope. If you're laying gravel for a landscape path, you might prefer a flat surface all the way. From the bare dirt, determine how many inches up you need to build with gravel. For example, the flat path might need three inches of gravel all along its course. The gravel driveway might slope eight inches from start to finish and might require three inches of gravel all around, but it wouldn't be level from start to finish.
Drive stakes into the ground on either side of your project at the different height you need to hit. Begin at the top, driving your first set of stakes where your gravel starts. Put one pair of stakes every 12 to 18 inches so you can check your work. For the projects above, you would drive the stakes three inches above dirt; this would be level all the way across for the path and sloping gently for the driveway.
Lay your gravel along the path, estimating its height by checking your guide stakes. Rake the gravel over the area with a landscape rake. The gravel should rest at the top of the stakes, no lower or higher. Until you lay the gravel, you can't check to see if it is level.
Lay a metal straightedge over the stakes at the beginning of your project, so it sits atop both stakes. If the gravel is level, it should rest against the belly of the straightedge without pushing it up. If the gravel is too low, it won't meet the straightedge. If the gravel is too high, the straightedge cannot rest on the stakes. Adjust the gravel level accordingly.
Rotate the straightedge clockwise, turning it. Make sure it remains level as you spin it; you'll know the gravel is level. If you encounter peaks or valleys, remove or add gravel until you get a level fit.
Pick up your straightedge and move to the next set of stakes. Test the grade in the same way. Continue down the line like this, checking that you have levelled your gravel.
If you don't have a metal straightedge, use a very straight piece of wood for your drag.