Should I plant daylilies all at once in different varieties or better to start with one?

I'd start with one or two varieties to see how they settle in on your plot specifically and what kind of care they need! Daylilies are generally pretty low-maintenance, but each one can prefer its own moisture level, light, and soil type. Once you figure out how they do, it's easier to add new varieties later and not worry about killing them off with the wrong conditions.