DB Connect into BW

Hi,

I have a requirement where data from third party source system(thru DB connect) should be staged and reported in BW/Bex. There are more than 30 tables involved in Source system and i know their relationships as well to create 10 reports as user needs.

Now i need to give solution architecture to stage this data in BW before going for the reporting in Bex. Please help me to know how many DSOs, Cubes etc.., i need to stage these data for better modelling in BW.