Ok, first prototype...
Casino
Cost: 5
Treasure
+1 Buy
Reveal the top three cards of your deck. +1 coin for each treasure revealed.
If you reveal three of the same treasure, you may thrash this card and play the treasures in any order.
If you reveal three differently-named treasures, you may trash this card and play one of them.
Discard any revealed treasures which were not played and put the remaining cards on top of your deck.
Unless you hit 3 treasures, this is a Woodcutter at best, and a Ruined Market at worst. Keep in mind that even in a deck that's 80% treasure, you only have about a 50-50 shot of drawing 3 treasures at the top of the deck.
If you do hit 3 treasures and don't trash, it's +1 buy +$3, which is probably a little weak for $5 (it's a Horse Traders without the discard but no reaction). Margrave is usually stronger, since you usually have an average card value over $1 plus it has the attack. At any rate, you're pretty likely to not be able to trash, since you probably won't get 3 of the same card OR 3 unique cards - you're probably most likely to get something like two coppers and a silver.
If you hit 3 treasures and do trash, it'll usually be +1 buy +$6. I don't think it's usually worth it to trash a $5 card just for an extra $3 to spend. Consider that Mining Village can be trashed for +$2, but also costs less and has a weak on-play effect (just a regular Village). Trashing a Casino is like using a Spoils that you had to spend a turn actually buying.
This card seems like a big-variance card (which you're probably going for with Casino), but it seems too big. Half the time, this card is a Woodcutter or worse. The other half, it's a terminal Gold, or a even single-shot for a huge payout. I wouldn't pay $5 for something that half the time is a $3 card or worse. I guess it could work in Big Money decks, but it becomes a big liability once you start to green. Its effect quickly degrades to Woodcutter levels, and you won't be able to trash it once it stops hitting. Come endgame, I'd rather have a silver. If this card could be fixed so that the no-payout option wasn't so bad, it might be a start at improving it.