What is the cheapest substance to use to engender a nice looking curb around my driveway? I have a massive circular driveway and when I moved in, it...

I have a massive circular driveway and when I moved in, it have old railroad ties as border. Well, superfluous to say, most be rotted so we had to nick them to the dump. Now, we have no border. I hold a gravel driveway and can not afford to pave it but I thought a really nice curb and some nice landscaping would spruce up the front patio. Any suggestions on what to do to make a nice looking curb that can be contoured into a partly circle?
Fertilizers? School project??
Answers:    For a residential driveway, nothing will remodel the appearance like brick or paving stones. Wood, within my opinion, is not attractive and creates problems within mowing, and will eventually need replacing.
When populace drive beetle why do they own...
Some low growing juniper or heather would look nice, and would minister to to keep your gravel intact. The cheapest substance I use a lot of is wood, return with some good sturdy wood, cedar etc, and split the logs as long as you need them to still trademark your circle. The wood color is nice and it rounds into the garden well. I love creeping thyme on the edging and in the cracks to stamp the border, comes in several colors. Other cheap items, stones, bricks, or even stumps possibly would suffice.