How did God provide for the poor believers in Jerusalem after their common fund ran out?
After the Jerusalem believers' common fund ran out, God in His grace and goodness provided through the collections Paul took wherever he went. These were gathered for the poor saints in Jerusalem, because the shared kitty had emptied and new believers were not refilling it fast enough.
Les explains that this early called-out group of Jewish believers lived out of one common kitty, but without high interest it depended on new believers adding to it. When it ran out, God in His grace and goodness covered the need through Paul's journeys: wherever Paul went, he took collections for the poor saints in Jerusalem. They were poor because the kitty had run empty and new believers were not filling it fast enough.