Activity Based Costing

I am a student and I am working on a project to analyse variant induced complexity costs in a high mix manufacturing environment. The entire product portfolio is very complex with even thousands of diverse parts under certain product types. To identify the impacts of complexity on costs, I am planning to run an Activity Based Cost analysis. But, due to large portfolio, I am not getting a clear idea on how to begin and proceed step by step or what data should I begin to collect etc. Should I do value stream mapping to trace entire sequence of activities? Or Do I just list activities according to the various departments or on any other basis?

Any guidance in this case as to how to proceed furthur will be appriciated.