Using a list to manage approval workflows

Question

I don't know if I'm just not providing the right serach context but I am trying to learn how to use a list to store users names (people and groups column), office/department column, workflow approval step ie manager/senior manager for assigning a task. Everything I find on the web refers to either using user profile service or lookup lists. I want to use a lookup list but I don't want the initiator to choose a approver(s) instead I want them to select the department they belong to and the logic in the workflow routing to be able to select the manager/senior manager which match that department. I feel like once I figure this out everything else (in several other use cases) will come together (I hope).