Suggestion for wording:
Recover, Action - Duration, $0
At the start of your next turn, draw until you have 5 cards in hand, then +2 Cards.
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You can not gain this if you gained another card this turn.
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When you gain this, play it and end your turn.
Sadly, this wording also doesn't avoid the second line, but at least it's mostly old mechanics. The only difference would be that Grand Market forbids buying, not gaining, but it's basically an automatic Trader reveal. Oh, and you can buy it after gaining something else, but that does nothing.
Also, i think it's a bit weird that you try to make sure this card allows for practically nothing else on your turn, but, on the other hand, intentionally made the wording more complex to ensure it stacks. I'd probably go with simply "up to 7".
Edit: Also, i should probably point out how similar this idea is to Expedition. Discard attacks aside, it's also much weaker in my opinion.