I made the armor first because I was rocking troll hide at the time, but with the benefit of hindsight I say make the boat first. You fill up the karve, take it back, smelt all that, make the boat and maybe armor or weapons, or base upgrades depending on your priorities and how hard you're finding the combat. Then you can take the longship back to your swamp and clear the entire rest of it in one go. Will probably take you a couple days IRL if you're playing 4-6 hours a day, but you'll come back with upwards of 600 iron and you WILL use it all.