How are you expecting people to use that second card? To get any really nifty benefit from it you need to be playing two or three, which involves having two or three other cards in hand to trash with them. Doesn't that mean you either have to incorporate it into a fairly powerful engine which can do plenty of nifty stuff anyway, or people will end up turning Copper and Curses into Copper and Curses until two piles are empty? (-8
I've floated around a couple of variants before settling onto this one. 'Up to' could be 'exactly', 'Gain a card' could be 'You may gain a card', 'the number of [Card name]s in play' could have 'after the first one', et cetera. They are initial concrete versions of concepts I thought of, not final versions.
Yes, it needs an engine to get two or more of them. And yes, you can't trash Coppers with it. You're right on both accounts - perhaps it's too weak. I think the most interesting fix would be changing it to 'Trash this or a card from your hand' like Raze. I use 'up to' instead of 'exactly' to give the player more control when playing multiple.
I think allowing it to self-trash so you don't need an engine for more than two, would make it more interesting. Let's also allow for Copper-trashing to see what happens:
[Card name]Cost: $2. Types: Action.
Card text:
+1 Action. Trash this or a card from your hand. You may gain a card costing up to $X more than it where X is the number of [Card name]s you have played this turn.
With just one it's worse than Raze. In multiples they become stronger (and don't need an engine). You could turn Estates into more of these to get more benefit. Maybe this new version could be $3. I'm not sure.
On the second: I use 'exactly' so it can trash Coppers and Curses. I could've used 'You may gain a card costing up to $1 more than it', but it's more wordy. The Reaction is useful with trash-for-benefit or when you want to turn a card into another card. Don't forget having two of these lets one react to the other.
Yes, they aren't very strong. I was trying to make cheap cards.