What is the ruling on a light drop of prostatic fluid (wadi) exiting after waking up from sleep, and what exits with urine from it daily? And does it necessitate ghusl (ritual bath) or wudu (ablution) and washing the garment?

What you see after waking up is not wadi (prostatic fluid), because wadi is a thick, white fluid that exits with or before or after urine. It nullifies ablution and is impure, requiring the washing of any clothes or body parts it touches. If what you find matches the descriptions of maniy (seminal fluid), then it is a wet dream, and in this case, a ritual bath (ghusl) for major impurity is required. Washing clothes or the body from maniy is recommended, not obligatory. If you do not know what fluid has exited you, refer to Fatwa no. 66589. What exits with urine is most often wadi.