Lesser Healing Potion

The Merchant sells them from the moment he moves in, which alone covers most of an early run. On top of that they turn up in pots before Hardmode, in generated chests, in Wooden Crate and its Pearlwood equivalent, and most of the early bosses drop a few when they die. The Skeleton Merchant carries them on the even moon phases if you meet him underground. Buying rather than brewing is usually the right call this early.

The heal is modest and the lockout afterward is long, so this is not a way to out-heal incoming damage. It is one reset per fight window and no more. The standard beginner mistake is drinking the instant you take a scratch, while still near full health, and then having nothing when the boss actually connects. Hold it, back off, and take it when the heal will not be wasted.

The lockout is one of the few debuffs an accessory can cut short. The Philosopher's Stone and the Charm of Myths both do it, but both belong to Hardmode, well after this tier has stopped being your main heal. Until then the timer is fixed and you plan around it.

This is the bottom rung of four, and the lockout is the same length whichever tier you drink. That makes the upgrade path mandatory rather than optional: once Healing Potion is available you are wasting your one window every time you drink a lesser one. Keep the leftovers for spelunking, where the small heal is fine and you would rather not burn the good stock.

Placed potions on Dungeon platforms, usually next to Lesser Mana Potion bottles, are not decoration. They count as a bottle crafting station, so you can brew on the spot instead of hauling one down with you. A pickaxe or an activate press frees the potion itself if you want it. If you want the look at home, they craft into the Decorative Healing Potion.