1-2 pounds of berries is about right. Must admit, I've had gooseberries, but not recently enough to remember what they taste like. The basic recipe looks fine and you can always add more berries later.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk