Minecraft wiki entry for Drowned_farming, associated text: Several full stacks of cobblestone
If you can get a lava bucket, you can make a cobblestone farm to get an endless supply
You need cobblestone blocks not only for building, but for making stone pickaxes to harvest cobblestone from the farm, and to make stone stairs for getting around the top of the farm, as well as stone slabs to prevent mobs from spawning on exposed horizontal surfaces
4 to 5 full stacks of glass blocks; this may be the hardest material to collect without a desert nearby
A couple stacks of ladders or scaffolding for climbing back up your farm if you fall during construction.
A hopper (optional, but makes collecting loot easier)
A chest (preferably two for a double chest)
A handful of buttons or signs to control water flow
A stack of slabs
Two water buckets
At least 2 or 3 torches