Good macro lens, Nikon D5100, for $200-250?

^^^

Have you visited the Nikon website?

You will see that $200-$250 is an unrealistic figure for a macro lens

http://www.nikonusa.com/...index.page

Remember that you will need AF-S lenses in order to use full auto-focus with you fine entry level dSLR

Here is the least expensive Marco lens.

http://www.nikonusa.com/...F2.8G.html