From a medical standpoint, your shoe is the most important past of your outfit and the part that most touches the earth.  It is important to protect your joints and body with good cushion.  However, while flip-flops are fine inside the home, outside the home they can put subtle repetitive strain on the body to keep them on your feet.  For best results your usual and every day shoe should be well-cushioned and secure on your feet so you are strapped in.  Invest on good shoes.

Road Runner Sports

Comfort Wide Shoes & Orthotics

The Cloud Collection

Clarks

Ecco

Hoka

MBT

Skechers with goga (yoga mat rubber sole)

Happiest Baby on the Block