When it comes to plunking down a few 5-figure checks to purchase and implement your DAM, having your management solidly on-board and understanding its benefits needs focus and attention, perhaps before most other things.
To that end, a https://www.resourcespace.com blog has two articles, the first entitled “8 ways manufacturers use their DAM to save time and money” that can serve as a good base template for your business case, and for material for a DAM charter, financial justifications, and C-Level and stakeholder presentations explaining why they need to invest significant finances and effort: each of the 8 concepts applies to any industry considering a DAM, not just manufacturing.
It is a bit more detailed than their October, 2018 post, Building a business case for DAM, but the two articles work well hand-in-hand.