I started writing this up after my last post, so you might have already addressed some of these. Don't take this criticism the wrong way -- it is meant to be constructive. There are some neat ideas here!
There are also some completely broken ideas though.
Mortgage -- I imagine this is pretty strong. Often you should be easily able to afford a single discard in your next turn. Moreover, it wouldn't be too bad to just spam a bunch of Mortgages. After getting +$5 with Mortgage, you know your next hand is wiped out anyway so you might as well keep playing them. In weakening one hand to improve another, Mortgage is sort of like Tactician. But it is cheaper, gives a bit more control, and it gives you to the benefits now (which tends to be better than getting them later).
But overall, it is hard to evaluate. It might be OK. There is a tracking issue in that you have to remember how much money you gained with it so that you can discard the right number of cards. The major problem is that you have to remember it on your NEXT turn, which is longer than most cards require you to remember something.
Accountant -- people have already mentioned that "value" is not always defined for treasure cards. Also, you have to be careful about order of cards revealed. You'll notice that there aren't any Dominion cards that do this. They either discard everything else (e.g. Golem, Sage) or they let you put cards back in whatever order you want (e.g. Oracle). It's pretty easy for a player to mess up the order by accident (or to mess with it on purpose, for that matter).
Another issue is, what happens when you don't reveal a treasure (maybe because you don't have one in hand)? From the current wording, it is undefined.
If I am understanding the card correctly, Accountant is pretty weak, which is appropriate for a $2 card. To fix the other problems, I would start it, "You may reveal a treasure from your hand. If you do... until you reveal a treasure with a different name... shuffle the other cards and put them back on your deck".
The last part of that is because, again, requiring the same order can have issues. But you also don't want to let the player put them back in any order, because then one of the best (and most annoying) use cases would be to reveal a set it up so that you reveal your entire deck, allowing you to re-order it as you please. It would be easy to do actually -- just don't buy any treasure, so your deck only has Copper.
Casino -- no need to call out Curses specifically. Do you mean for the bonuses to stack? For example, if I reveal 3 Coppers, Casino will give me a total of +2 cards, +2 actions, +$5. If you don't mean for it to stack, it should be written:
"Reveal and discard the top 3 cards of your deck. If all 3 have the same name, +2 cards, +2 actions, +$2. Otherwise, for each action card..."
I like it, but I think it is undercosted. It should probably be $5, but $4 at least. It is very comparable with Harvest.
Convention -- the wording is off. For this kind of effect, it is "while this is in play", not "in games using this". So:
"While this is in play, you may gain a Convention when you gain an action card costing $5 or more."
Anyway, this is a cantrip that becomes a Peddler from the third play onwards. That feels weak to me. As a baseline, a regular Peddler is costed correctly at about $4. This is slightly cheaper but takes significantly more effort to activate. It does have a clause to let you gain more of them quickly, but that requires investing in a bonus-less cantrip in the first place.
This is probably an OK card, but definitely test it more. I wonder if it would be better at $2.
Deflation -- some wording issues again, and there is the problem of treasure "value" once more. I don't think there is a way to fix it and retain the same concept (which, for the record, I think is extremely powerful and probably warrants a $6 or $7 card cost).
Investment -- big, big tracking issues. It's already difficult for some people to track regular Durations. One that lasts a second turn? super confusing!
Secretary -- extremely powerful. Consider the two most common use cases, especially at the start of the game:
A) +2 cards, discard a copper, +$2.
B) +2 cards, discard an Estate, +1 card.
Case A is net equivalent to +2 cards, +$1. Early game, +$1 is worth about the same as +1 card, so this is very close to case B...
Case B is basically +3 cards because that Estate probably wasn't doing anything for you anyway. So it is a Smithy! And Smithy is a $4 card.
I would try testing Secretary at $4 to start, potentially increasing it. It really looks too good for $3.
Teller -- "same order" has issues, as noted above. I'm not sure if this is OK at $3 or if it should be $4.
Charity -- Your opponent would never reveal a hand with no treasure because there is no place for them to do so. You tell them to discard treasure or gain copper, never to reveal their hand. But a bigger problem is that this is a powerful cantrip attack. There are very, very few attacks that are non-terminal. Off the top of my head, the only ones are Spy, Scrying Pool, and Urchin. The first two are simple deck inspection and don't stack well (once you leave a bad card on their deck, additional attacks don't do anything) and Urchin only drops you down to a 4 card hand -- not scary at all. But this one is Cutpurse or Copper-junking, both very painful.
Insiders -- Very interesting concept. The main issue is, again, tracking. I would rephrase it like this:
"At the start of each other player's next turn, he gets +$2 and +1 Buy. While this is in play, when another player gains a card, you may gain a card costing up to $2 more. At the start of your next turn, trash this."
That way, the card remains in play for tracking purposes until your next turn. Also, you don't have to say "buy or gain" because when someone buys a card, they will gain it. If you say both, you would be able to gain two cards for their one buy.
There is one other big issue with this card -- infinite loops.
Amy and Bill have both played Insiders. It is Carol's turn. Let's say Carol buys a Copper. Now Amy and Bill can both gain a card costing up to $2. Let's say Amy gains an Estate. OH HO, now Bill can ALSO gain a card costing up to $4 due to what Amy just gained! But when Bill gains something from his Insiders, Amy's Insiders will trigger again... and then Bill's... and then Amy's... so by buying a measley Copper, both Amy and Bill drain all the Provinces, not to mention the rest of the supply. And of course there are some issues in figuring out what order they do all those gains in as they bounce off of each other...
So I would do this:
"While this is in play, when another player gains a card, you may trash this to gain a card costing up to $2 more. At the start of your next turn, discard this."
The core concept is still intact. Infinite loops are gone. It is trackable. Opponents no longer gain a bonus because that could become pretty confusing -- do they still get a bonus if you have already trashed it away to another player's gain? So just cut that away entirely. And if you haven't used it by the time your turn rolls around again, you get to keep it.
This new version of the card isn't very powerful. Your opponent can easily play around it. But it would add some interesting interaction. You have Insiders in play... now I have to weigh whether it is worth it to buy that card if it means giving you an even better one.
Landlord -- cantrip attacks again, noooo. Like I said above, Peddler is already a $4 card. Now you've added an attack on top of it, and a decent one at that. Even with hurting yourself via Estate gains, this is too powerful.
Speculator -- Too powerful. Far too powerful. This is Highway with +Buy, which is just brokenly powerful. The next turn penalty does not matter at all if you end the game this turn.
There is a bit of a tracking problem in remembering whether that Speculator was played this turn or last turn, though that's not really worse than any other Duration.
But yeah... too powerful.
Embezzlement -- there is an accountability problem in that you need to have "or reveal a hand with no treasure". There is also the issue of treasure "value" again. And there is an issue in that this is basically a super-Cutpurse. Cutpurse can be really bad but at least it only kills Coppers. Embezzlement makes pinning players much easier. And that's before considering that this is a TREASURE attack, which means it is trivial to play multiples in the same turn.
And I'm not sure what you mean by "$1 Buy, $0".
Deposit -- how are you going to track how often it is played? Tokens, probably, but we already do have Victory tokens for Bishop, Goons and Monument. So this card is kind of like:
+1 Card, +1 Action, +0.20VP.
So this is a cantrip VP gainer... that can be bad because it leads to games that never end. Say both players just play chains of KC-Deposit to rack up VP... how will the game ever end? Note that this issue can come up with existing cards (KC-Monument, or Bishop spam on Fortress) but those are less likely because they are terminal and they provide money which encourages you to buy something, moving the game state closer to an end. But with Deposit, all you get is VP.
Granted, it is much slower.
Oh, unless each Deposit is worth that much VP. If so, then having 5 Deposits makes each play +1 Card, +1 Action, +1VP. So the problem is bigger!
Presentation -- not sure how it compares to Tribute.
Stock Exchange -- I think it is OK.
Shipment -- Tracking issue. With this card, you pretty much have to keep a running tally of how many treasures are in your deck, because it is not feasible to count them all every time you play Shipment (it would be more annoying than Philo Stone, but it would also require you to look at cards which you shouldn't otherwise be able to look at!). But keeping a running tally isn't always possible -- consider Masquerade. If I play Masq and pass an Estate in a 4p game, I will have to reveal to everyone that I passed an Estate or else the tallies for me and the player to my left will be incorrect. I don't think there is a way to fix this card without heavily altering the concept.
Con-artist -- If you want to use Ruins, you have to give it the Looter type. The Con-artist restriction is not necessary because you have it costing $6 but only gaining up to $5. OK, it could matter in conjunction with price reduction... but then, the better wording is "gain an action card costing less than this".
I think this looks OK.
Liquidator -- super confusing, and yeah -- very political.
