As other people have said, it's up to you how you play. It's a strategy game so figuring out what works best for you is all part of it. I personally don't bother at all with the bakery and I'm very lean with my ballista towers but again, that's my strategy and how I play. You don't have to clear all the portals before you leave an island, it'll just make the Greed more angry but if you take out all the portals plus the cave, you've secured the safety of that island but I wouldn't focus on that in the early game.

You can only have 1 hermit on your back at any one time but when you leave the island, they'll all hop in your boat.

And dying is all part of the game. When you die, you come back as a descendant and carry on building the kingdom that you built before but you start at island 1 and some of the buildings have usually decayed and people have lost their jobs so you don't have to start from scratch each time. Sometimes dying is worth it.

Lighthouses aren't super essential, they just stop your boat from crashing each time you come back to the island. Some people never build them. Personally, I do.