D2C and Inventory Modeling

Hi everyone. Asking the community for some help on a couple of projects...

1. I'm helping a D2C apparel portfolio company revamp their model so it's more investor-friendly before they go out and raise another round of capital. Since their main sources of revenue stem from FB and Google Adwords, I need to help them figure out what KPI's are particularly important for them to track and showcase. Part of the challenge too is that a customer ordering from FB may have some attribution from seeing Google Adwords and vice versa. Does anyone have a D2C model that ties/tracks marketing spend to revenue based on marketing channel? Any best practices you guys could share or KPI's you find particularly important?
2. I'm helping another company in the beauty space create a spreadsheet model that allows them to better forecast inventory. Since a product typically has multiple components that have various lead times, it's important to understand bottlenecks, optimal order quantities, what components are shared across multiple products, etc. This is basically a supply chain/inventory planning exercise. Does anyone have experience with this or has a template/model I could refer to?

Thanks if anyone has insights to these or can refer me to someone appropriate