The Targum Pseudo-Jonathan specifies the three gifts that most moved Jethro: "Jethro rejoiced over all the good which the Lord had done unto Israel, and that He had given them manna, and the well, and that he had saved them from the hand of the Mizraee" (Exodus 18:9).
The Aramaic singles out the manna and the well (the well of Miriam, which traveled with Israel through the wilderness) as the wonders worth naming alongside the exodus itself. Why these two?
Because they are the wonders of ongoing provision. The exodus from Egypt was a single spectacular event. The manna and the well were every day. Jethro, as a former priest and a sensible man, understood that any god can make a spectacle; only the real God sustains a people in the desert for forty years with bread from heaven and water from a rock.
The Targum's word for rejoiced carries the sense of a man whose long search has finally ended. There is something wrenching about a father-in-law from another nation, older than Moses, coming to this conclusion about Israel's God before many of the Israelites themselves had stopped complaining.
The takeaway: the spectacular miracles catch attention, but the small, steady ones — bread each morning, water each day — are what convert the thoughtful heart.