The pirateship is the end of the patreon build for now. Fire Dungeon is in the Beach Cave, you need to finish a quest you get after finding a big red crystal in the beach cave. Won't spoil anything else!
Rubies are not related to the Fire Dungeon. If you follow the story you'll walk past a closed door that's where the dungeon is. You need to find a "BIG RED CRYSTAL" in the beach cave and then do the quest related to that to open the door.
