Dominion: Prosperity
Depending on which way you look at it, Trade Route is either a useful card throughout the whole game, or a card that anti-synergizes with itself. The forced trashing ability is quite valuable early but a pain in the late game. But it doesn’t provide any money until the late game, and the +Buy is equally useless unless you have enough money to make it worthwhile.
In general, Silvers are preferable to Trade Route if there are other sources of card-trashing: Chapel and Steward are much faster, and Bishop and Remodel can provide bigger benefits early on. But deck-thinning is important enough that Trade Route is probably worth buying if there are no other ways to do so.
Naturally, Trade Route is most powerful when there are Victory cards in the Kingdom set, because those are usually popular enough that you can get at least some money off of the Trade Route early on. The presence of Hoard also greatly incentivizes players to pick up Duchies and Estates in order to gain Golds.
Trade Route is also useful in a hybrid Gardens strategy, taking the place of Woodcutter or Workshop. Even though it requires a card to be trashed, thus lowering your deck size, the +Buy helps make up for it. More importantly, a Gardens deck that concentrates on Gardens and Estates can guarantee at least +$2 on the Trade Route, and often $3 or $4 if Great Halls or Nobles are present. Opponents are also forced to buy Victory cards earlier than they would otherwise in Gardens games, further increasing the value of your Trade Route.
Works with:
- Hoard
- Nobles, Gardens, Harems, Vineyards, and Great Halls
Conflicts with:
- Treasury, since people will be discouraged from buying Victory cards
- Chapel/Steward, since they are better deck-thinners, and Trade Route’s forced trashing is more likely to be a liability
Dominion Strategy 
And of course, the blindingly obvious: it works well in any curse heavy set. Particularly if Mountebank is seeing heavy use.
I think you underrate this card. It ramps you up fast in the early game by trashing Estates and Copper, and in the endgame it lets you cannibalise your deck to buy extra VP cards.
If you have an abundance of +2 action cards, Trade Route can be nice with Goons, because it trashes one of those Coppers that are clogging your hand, provides extra money and another buy, thus another VP coin.
after moving a token from a victory card to Trade Route, do you replace the token on the victory pile with a new one?
No. This means that in a game without Kingdom Victory cards (e.g., Island, Nobles, etc.) and without Colonies, Trade Route will be worth $3 at most.
Do each Player has his own Trade Route mat and each one gets his own set of tokens? What is the limit of different Victory cards a game can have?
There is only one Trade Route mat that counts for all players.
There is no limit of different Victory cards (even after more expansions due to Black Market). Currently (up to Cornucopia) the theoretical max. value for Trade Route is 12, if I count correctly.
Try 15 😉
Estate, Duchy, Province, Colony
Vineyard, Fairgrounds, Tunnel, Silk Road, Framland, Great Hall, Duke, Harem, Nobles, Gardens, Island
Seems like the counters don’t go on black market cards since they’re not in the supply. So it’s a kingdom with trade route, 9 vp cards + estate, duchy, province, colony = $13. (Reyk probably just missed the colony.)
Does trade route work well with Duke? I know Duke doesn’t usually like trashing, but it adds another green pile, and Duke/Duchy strategies benefit from +Buy and tend to have a lot of junk in the deck.
Seems like it would work ok if your opponent is going for provinces. It wouldn’t be that hard to get it to $3 (duke, duchy, estate), and once your opponent gets provinces it’s worth $4. You’re going to want to hit coppers with it (so subtract $1 from its value), so another source of +buy would be helpful. (Losing the coppers won’t be a problem since you just replace them with the +1 buy.)
On reflection, it’s not worthwhile unless its worth $4 or more. If you’re trashing a copper to get $3, then the trade route is worth no more than silver. Plus, it has to find a copper (or estate), so it’s a bit worse than silver.
$4 Trade Routes are probably also better for a Province player than the Duke player. First off, all in all he is really more likely to have a use for all that money. Second, he benefits a lot more from the deck thinning. Third, it’s an easy third pile to run out, which could potentially work in his favor. And fourth, he might even be able to buy Duchies and trash them to spite you and/or shorten the game. (In a pinch he might even trash his Provinces to shorten the game.)
Or to put it more simply: a high-powered Trade Route is a strong endgame card. A Duke/Duchy slog doesn’t want to play against a strong endgame card; it wants to play against a deck that chokes in the endgame. Stronger, engine-based Duke strategies might handle this better; I don’t know.
I feel as if it would work well with Islands because they promote other players to buy VP early (and also because its another VP card)
With Dark Age’s Shelters, I believe it’d be safe to say this card is somewhat better since Necropolis lets you play up to 2 of them without collision, and players may be more incentivized to buy Victory cards to trash the starting Hovel.
Conflicts with Golems… I’ve played Golems in decks I shouldn’t have had (e.g. Masquerade’s forced exchanging/passing), and Trade Route can really hurt you.
So if you buy a victory card with your first buy, do you get an extra coin to spend on your second buy? The rules don’t address this.
No, the amount the trade route is worth is determined when it is played.