The wording still is unclear. To mean what you try to express, it should be:
When you would gain a card during another player's turn, you may reveal this from your hand, to instead discard this and any number of non-Action cards, and then draw as many.
I'm sorry to say, I don't really like it. It seems slow to resolve, and during another player's turn on top of that. It also has a lot of words, and generally speaking, I don't think additional would-gain cards similar to Trader are a great thing. Even Donald has expressed regrets regarding the rules-mess of Trader, whereas he doesn't mind Watchtower. 5$ and a Potion is also really expensive, too expensive for the trashing to be useful, as it will become available only late game, where trashing is usually bad. Also, the attack is arguably worse than Witch. The Copper junking also keeps going and going, which is usually considered poor style, but again, it happens very late, so it might actually be fine for opponents who have started greening. Finally, the card has a lot going on. It trashes, it junks... Considering how late you get this and that it is terminal unless you trash with it (which, as stated, is less easy late-game), you can't even chain it that well, which again isn't that great a fit for a Potion card.
I know you love Potion cards, but I feel this really doesn't want to be one.