What is the best file structure and tagging structure?

You can use whatever structure you’d like. You can even import your current file structure directly (from server, for example). However, with DAM systems, it’s more efficient to use Keywords (overarching categories) and tags (granular descriptive words) in place of complicated file structure. In fact, you could load all your assets into one album if you want to, and only filter by Keywords and tags to find things.