You can even make a basic stone generator (using glass, lava, and water) if you don’t feel like mining for stone or cobblestone.
Fences are useful for making turrets at the tops of towers.
Building a mansion over the cave can add even more fun. Use Redstone or other clever tricks (command blocks, if you hack your game) to make things like an elevator that takes you down to the cave.
Wool makes good sails for a pirate ship.
Building the exterior first also has the added benefit of letting you get the ceilings up, which means you get to stay out of the rain and snow.
Minecraft Building Inc is one great example.
