You can use any yarn and any size needles for this, gauge is not critical.

I love diagonally worked washcloths, but garter stitch gets boring after a while, so I took out an old stitch dictionary I had and started adapting them to washcloths. This is the first in a series.

The great thing about working diagonally is that you can make your cloth any size you want. As small as a washcloth or as big as a blanket! Great for afghan blocks too.