Hi Sheila,
Number of parameters depends on your watershed condition. If I was I would try to understand my watershed hydrological processes, even understand all my subbasins hydro process and find which subbasin assign more weights to flow generation! try to study same research papers which studied in the same hydro/soil/land use systems (particularly Dr Karim's papers) and check all their parameters for your case, you should be able to match up with your watershed condition in a case of stream flow (I amnot sure if it is your case) simulation!
In my case, I never included snow parameters in the model process as we dont get snow over my watershed. But I included ground water parameters which contribute to river flow in dry periods. Field based experience can give you more idea about watershed behavior as well.
Hope this gets you started.
Best,
S