Men of which tribe "understood the times and knew what Israel should do"?

Answer: Issachar

Among those who came to make David king were 200 chiefs of Issachar who understood the times and knew what Israel should do.

“From Issachar, men who understood the times and knew what Israel should do: 200 chiefs with all their kinsmen at their command.”— 1 Chronicles 12:32 (BSB)