You suddenly find yourself flooded by stimuli you never new existed. You will see the ground beneath you like you have never seen it before. If this is your first time and you wish to carry shoes with you, then do so. However, we encourage you to at least try hiking barefoot. Don't ever say we didn't warn you.
Amount depends on the hike length, difficulty, and time of year.
Rain gear or jacket depending on the weather. First aid kit. Food depending on hike length. Insect repellent depending on the season. Means of carrying the above.