I like to use relaxing oils to soothe my feet after a long day. My favorite combination currently is lavender and chamomile. Mint is also a great one to use, as it can be very up-lifting. Breastfeeding mothers should avoid peppermint, because it may decrease milk supply.  If your feet will be in the sun in the 12 hours after using the foot scrub, I would recommend not using any citrus oils as they can be photosensitive.