I used twice as many blackberries as honey in my last batch. I fermented the berries, pulled the bag, then mixed in the honey. How much water will depend on how juicy the berries are and whether you want a sweet product or a dry one. I'd aim for 2-3 gallons after removing the berries.
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