I am trying to create a wardrobe furniture piece where the materials on both the front section and case section change automatically.
If you already have all the materials, add them to the array, and cycle through the options. How to organise it would depend on how you need the cycling to work. I’d probably use a timer or a timeline with events if I needed a non-uniform pace of changes. Or something else if I needed the changes to match the beat of music, for example.
Can you produce an example?
- a piece of furniture with 2 sections, each with 5 materials?
- are we selecting something at random or is there a pattern?
- can patterns repeat?
- the materials are swapped every x seconds?
- how long is the showcase?
- do we need to show ALL available combinations?
Currently, it’s a bit too vague to suggest something tangible. There is also a question of scope, I’d approach things differently if this was a homework assignment for a single wardrobe piece with 50 combinations, and then quite differently if I had to re-imagine & digitalise IKEA catalogue entries since 2001 where they can inject new stuff on a weekly basis up until 2030. 
Do tell how it should work.
Dynamic Material Instances are for altering how a material looks and behaves at run-time. Not sure if that’s what you need; sounds like you want to swap out many existing materials instead.