For hard soils like gravel, hard pan, dense clay, limestone I've found that a good bargain can be had at the big-box home center. Check out the aisle that has vinyl siding and fittings and look for giant aluminum nails sold as "skirting spikes". They sell for about $.50 each out the door. They are often sold in bags of ten.

What you get is a giant aluminum nail that is about 1/4" diameter, 7" long, and heavily textured with chevrons that help it resist pull-out. The head is sturdy and at about 9/16" diameter it is wide enough to keep light line from sliding off. The aluminum is stiff and hard enough to hammer reliably in anything short of solid rock.

In sand, snow, and softer soils aluminum angle-stock is easy to manufacture into your favorite stake design. A hacksaw and file are all the tools you need.

I've had good luck in light/casual use with commercial plastic stakes. They are cheap and easy to find. Most big-box discounters sell a no-name version that works well enough but all of them tend to get brittle over time and most can be tender in deep cold.