mustard, and dill are a bit tricky because you need to sow the seeds in soil or some other medium and then transfer the seedlings to water. For a simple herb stand in the kitchen, you can root herb cuttings in plain water in glass bottles. Avoid using chlorinated water directly as the bleaching chemical is not exactly friendly to plant tissues. Tap water that has been left to air overnight is fine, so is stored rainwater. Spring water or well water is the best because it has some amount of dissolved minerals that may be of use to plants.