You CANNOY feed leather! Leather can only absorb something like 5%. All these oils and balms are doing is making our leather greasy, which in turn attracts dirt which 'polishes' the leather giving you the shiny effect.
Get some All purpose cleaner from tesco, mix it 10:1 with water and use it to scrub the leather gently with a nail brush.
The once a week give the leather a wipe over with a damp cloth.