Don't bother with soil, use peat moss or even better coconut coir fiber. Mix in a bunch of compost, dried out like AZ said and the worms will eat their way to happiness. As for plants, have fun, anything will grow in the once the worms have eaten a good portion of it. The CC fiber will make it easy to plant and easy to dig in there to get the worms out for fishing.

Just be aware that fertilizers can kill the worms in a closed container. So will a lot of pesticides.