I'll try to say a few things on the cards. In general, I would suggest you include images of your cards when you want feedback. If you want feedback, that is. If you don't want feedback, I guess I'm sorry, because here it comes nonetheless:
Astrologist: As Wero said, this is a delayed Ruined Library. Sure, you can stack a lot of them to get a lot of card draw at once, but you're basically killing your game for the mean time. That's never worth 4$. At least drop the price to 3$ and add an Action. About the reveal ability: I guess it means you know what you will draw before you do it, but as you'll have to draw that card sooner or later either way, the bonus is minimal. Not like the card allows me to sift past it. Also, it looks like it's supposed to interact with some other cards, but those are rare and the use of the effect is small.
Aztec Gold: Variants of this card have appeared here on fds countless times. A Gold that's cheap but curses you, hooray. The problem here is that on the first play of this card, the avarage coin value of the deck drops to a level below that you'd have if you had just bought a Silver. After that it goes downhill. Unless of course you have strong trashing. Generally, cards like this tend to be either too strong or too weak. I removed some of my own cards in the past because they had this issue. It's not really fun. A suggestion:
"Aztec Gold: Worth 3$. When you play this, each other player takes 1VP token."
This way, the card makes you fall behind in points every time you play it, but without clogging your deck. Probably it's still too weak, though.
Bargain: Why doesn't this just say "Trash a card from your hand. Gain an Action card costing up to 3$ more"? Oh, I guess because you might not want to gain the card you trashed? Also perhaps because it allows you to gain cards that have already been piled out (if they are in the trash now)? I'm not convinced this needs to be as complex. It's power is probably on the higher level either way, as you can make Coppers into 3$ cards and Estates into 5$s. On the other hand, it'll be useless sooner or later.
Blessing: This is another one that appears here often. If you have no more than two, they are only ever worth as a defense against Cursers. If you have more, you could go buy Curses yourself, but that would need a lot of buys. Again, I think this is too good when it's good, and too weak the rest of the time.
Cleaning Maid: This doesn't seem to do anything. With the exception of really specific boards and situations where it allows me to cause a three-pile, why would I wast a buy on this? It's not like my opponent couldn't just buy this themselves and return the cards again. The worst would be a situation where one player really wants the game to end and another wants it to keep going, e.g. because he needs another Province. They would just take turns emptying and re-filling the supply forever. I also don't see the combo with Bargainer - that card can just trash the target it wants itself.
Collective Effort: This card's idea isn't exactly bad. It's useless on boards without nonterminal cards, but a similar thing goes for Conspirator, and those boards are rather rare, either way. I don't see why it doesn't stack, though. Also, it maybe is a bit too similar and too easy compared to Horn of Plenty.
Contribution: I don't see anything wrong with this. The wording lacks a "when you play this", but that's a nitpick. In fact I kind of like this and think it adds something nice. Funny enough, I tried something similar with an Action card once (+3 Cards), but that one could discard anything and gained only Treasure cards. Yours is more flexible and can work for more boards
Imposter: This is too strong and comes close to being a directed attack. Early in the game, it will likely rob the player to your left of using their opening buys that shuffle. Sitting next to an imposter player gives one player an unfair disadvantage.
Investment: A bit too much text for me. It looks rather strong, but I couldn't say for sure it's too strong. Probably it's like Warf in that you want to consistently play many of these. It's a lot easier to do here than with Warf in fact, with the sifting and it being nonterminal. I can't see me discard an Action to this, though - simply because I'll likely already have plenty of Actions once I get this engine up and running. Then again, I'm not a good engine player.
Mermaids: Another one I've seen a lot, a Curse-Action. Ah well. First, the text is microscopic. Second, the idea that Duration cards don't do anything next turn if they are discarded from play inbetween is a misconception. The card staying out is a reminder only. If you e.g. use Procession or Bonfire to trash a Duration card after it has been played, it will also keep its effect. Third, are you supposed to be able to gain cards like Mermaids when a Witch is played? I assume not. Fourth, I don't like how this card allows you to trash a copy of itself to make each other player gain one and cause a 2-VP swing by that. If you use it all game long, you should have to keep the negative VP. Fifth, instead of using a new type, this could say "When you gain this, each other player takes 1 VP token.". The advantage would be that, while you still can use one Mermaids to trash another and deal them out to other players, you never get back that one VP you fell behind when you gained it.
Pirate Cove: This is too strong. It's a nonterminal Curser that even curses on gain. 5$ wouldn't be enough for this monster.
Pirate: I have nothing good to say about this. There's a reason Saboteur was removed from Dominion, you know.
Ravisher: Far too complicated. Very swingy. Also, in a game with many players, the chance to hit something gets smaller the more other players use this before your turn. I'm sure there's more, but it's really too complicated to wrap my head around just now.
Recruitment: This is fine. I wonder whether it would work better with a Menagerie wording that says "no duplicates".
Stock Market: I kinda like the idea here, but I think it's still rough around the edges. Perhaps this should not force you to play a Company. Rather it should make the play optional or give an entirely unrelated bonus instead. Technically, it could just pick a random card instead: "+1 Action. +1$ per every two cards that have been removed from the chosen pile. |Setup: Choose a random Action card pile in the supply."
cards drain something that is a prerequisite for getting the +
