Caroline.411

If you aren't that patient to come across it by clearing the islands, you can also buy them in the store. Just click the tab that shows the kind of money you get for clearing obstacles on the island (I personally refer to them as deblunes.) Provided you have enough of the currency, you can buy them there.

In the first archipelego, randomly. Go island by island. Don't visit the islands until before you are about to be granted new food and fuel, go to the island. Use up food and fuel. When you are granted new food and fuel, go and finish clearing the island. Clear one island after another in this way. You should find all the items you need to upgrade in the first archepelego.