For the intermediary items you will need the following raw materials: (which can all be found in the Buyers area of the market under 'tack, feed and raw materials')

Item	Materials
leather straps	2 pieces of leather
bit	1 iron
flattened iron bar	2 iron
cloth	5 thread
saddle tree	1 wood
saddle leather	1 leather

For tack you will need the following intermediary items and raw materials:
horseshoes - 1 flattened iron bar
saddle pad - 1 cloth + 1 thread
saddle - 1 saddle tree + 1 saddle leather + 1 wool + 2 thread + 2 glue
bridle - 1 leather straps + 1 bit + 1 thread
horse boots - 1 cloth + 1 thread