Lettuce greens, which include arugula, are fairly shallow rooted; they do not need but a couple or few inches of depth. More is fine but not necessary. See here for examples: https://www.almanac.com/how-grow-your-own-salad-greens
So you can use any size container but if you are growing other things, you might want depth to satisfy their root needs. You can search for individual vegetables on this web site (go to the top of this page for the search box) and learn more about each one’s needs.
Lettuce greens, which include arugula, are fairly shallow rooted; they do not need but a couple or few inches of depth. More is fine but not necessary. See here for examples: https://www.almanac.com/how-grow-your-own-salad-greens
So you can use any size container but if you are growing other things, you might want depth to satisfy their root needs. You can search for individual vegetables on this web site (go to the top of this page for the search box) and learn more about each one’s needs.