What I have found (with my 5c) is that it's best to go through your 'stuff'. Get rid of old photos, music, apps and such using a combination of straight deleting and iTunes. THEN- restart the phone, THEN do a manual backup, THEN do a 'restore' iPhone. When it connects back up in iTunes use that latest backup to restore the phone. You will get rid of a LOT of that "Other" space that isn't easily accessible otherwise. I easily recover a couple of gigs of space each time. Generally do it monthly just to keep ahead of any problems that can arise with so little space on device.