Copper Chainmail

Copper is the bottom rung of the ore ladder and the first set most characters ever put on. Make it as soon as you have the bars, because a small amount of protection counts for more in your first hour than at any later point, and it takes the first few nights from dangerous to merely tedious. A world contains copper or tin, never both. Tin is the marginally better roll, so if that is what your world gave you there is no reason to go looking for copper.

The helmet does one thing that has nothing to do with armor. Throw it at most slimes and the slime becomes a Squire Slime, a small joke enemy that only exists because you dressed a slime up. The Copper Shortsword does the same. It is a novelty rather than a tactic, but it costs one worthless item to see.

You will outgrow it fast. The set bonus needs all three pieces on at once, and the moment a chest hands you a better body piece you are choosing between the bonus and the upgrade, which by then is not much of a choice. Keep a spare helmet for the slime trick and stop thinking about the rest.