You might find lot of documentation on LSA on this site.
Staging is used for just to copy data from source systems.
Depending on the requirements, data quality, consolidation, complexity you might design one or two layers of staging.
You might need to dso layers to identify delta when the sources are sending full loads only.
You might need to combine two sources into one for flexibility in upper layers.
Rule - Copy as is, don't perform data transformation logic.
Gopi