It Depends on the oud really. Ouds react differently to the same string. So it is best to Experiment With many strings.
On my different ouds I have:
Aquila light C (tuned Down to B)
D'addario
Savares 10 string-guitar set, string #9
"""""""""""""""""""""""""""""""" String # 8
Thomastic
ghs string
But i did lots of experimenting before I found out what would work!