Why the order matters
Most visitors try to see every villa on the lake in a single day. It does not work, and the reason is not distance but timing. The villas open and close at different hours, the boat traffic peaks between eleven and two, and the light that makes these gardens worth photographing only lasts a couple of hours at each end of the day.
If you have one day, take three. Villa Balbianello in the morning, Villa Melzi around midday when its terraces are shaded, and Villa Monastero in the late afternoon. That order is not arbitrary: it follows the sun across the lake, and it puts you against the direction of the crowds rather than inside them.