The garden is really basic. I don't have fancy trays and don't spend a fortune on seeds. When I can I do buy seeds from a microgreen seed provider but, for the most part I use seeds that are available and cheap. Mustard seeds can be bought in most bulk food stores where it is sold as a condiment.
For the trays I use recycled water 6 liter water bottles cut in half and poke plenty of holes in the bottom. Above that I add a layer of compost, sow the seeds thickly, then add a thin layer of compost.
Depending on the season I sometimes water daily, other times two or three times a week. Microgreens grow very quickly so I usually sow more seeds, water, and harvest all at once.
Other days I simply run out to my little garden just as I am preparing to serve a meal and cut whatever I need with sharp kitchen scissors. It is good to rinse of the greens with filtered water just in case there is some soil clinging onto the greens.
Yesterday I made grain free "Canelones" with eggs, cheese, and shredded carrot. Inside they were filled with lettuce and topped with tomato sauce, cheese and, of course, mustard microgreens!
Do you grow microgreens? If so, what are the easiest and cheapest greens to grow?