Loading R/3 reference tables in MDM

Hi,

I would like to know how best one can load R/3 reference tables related to Customers in MDM thru Import Manager?

Options:

While loading for example KNA1 table whether all the required reference tables also can be loaded simultaneously thru the necessary mapping?

OR

First have to load reference tables(like Account-group,company etc) and then load KNA1 table's required fields to MDM

In this later case whether to map the reference fields also while mapping KNA1 fields which will try to create duplicates.

May be I am making some fundamental mistake to understand loading of reference/lookup tables and master tables process.

Appreciate your valued input

-Reo