Mint is a card with two very different abilities that synergize well with each other.
First, Mint’s “trash-all-Treasures” ability is a considerable asset in the early game when you need to get rid of your Coppers (or Loan). It’s less useful if you have good trashing through Chapel or Steward, but without other options (and especially with good card draw) it can considerably streamline your deck. (Keep in mind that you can selectively play Treasures; if you draw a Gold and 7 Coppers, you can play only the Coppers and use the Mint buy to trash all 7 of them. Indeed, with 4 Coppers and a Silver, it’s usually worth trashing the Silver to trash the 4 Coppers with it.) But buying a second (or third) Mint for the trashing is usually not that helpful; there are better terminal Actions, and unless you can Remodel/Salvage/Expand the extra Mints, it’ll probably end up getting wasted.
Occasionally, with a $5/$2, you’ll see people open with Mint to trash 5 Coppers. Personally, I don’t think it’s a great idea; you’re really set back by the loss of all those Coppers, and unless you have a $2 like Lighthouse, Embargo, or Pawn, it’ll be tough to get to and Mint Silvers quickly enough. It’s a viable option if there are no other $5’s, but probably not otherwise.
Of course, if you gain Mint (through Expand, Remodel, Smugglers, etc.), this ability doesn’t trigger. This is useful if good trashing has already thinned your deck into high quality Treasures.
Mint’s minting ability is more straightforward. It tends to avalanche; the more Golds you Mint, the more likely you are to draw Gold with Mint. Try to avoid using it on Silvers unless you have no other choice; bloating your deck with Silvers nullifies the whole point of Mint, which is essentially to run Big Money on steroids. Naturally, Mint works really well with Platinum; it also does well with other cards that benefit from high-quality Treasure decks (Adventurer, Venture, Grand Market) or lead to high-quality Treasure decks (Mine, Hoard). In the late game, when you can’t really count on the reshuffle, Mint is usually too slow (exception: Harem and Watchtower); look to Salvage or Remodel it instead.
- Platinum games
- In the absence of other trashing, can be a good way to get rid of Coppers
- High-quality Treasure decks (e.g., Mine/Adventurer/Venture)
- Treasure Map (trashing to activate them, Minting for additional Golds)
- Watchtower (which turns Mint into something like a Mine)
- Grand Market
- Loan/Talisman/possibly Quarry, if you have no need for them past early game
- Low-quality Treasure decks
- Very big decks that take a while to reshuffle
- Coppersmith, Counting House (although theoretically you could use Counting House to trash dozens of Coppers at once …)