I think Smugglers is actually a strong contender for "worst $3 card in the game", and rarely buy it. It has two main problems: first, it's a Workshop variant, so you're spending a terminal action to gain a card that may not be all that good. Second, it puts you at the whims of your opponent, and is only as good as their deck. If you're doing better than them, or pummeling them with attacks, then they're not going to be buying anything you want and the Smugglers is a waste. If they're doing well enough to buy important engine cards (that you want- Smugglers is obviously no good if you're taking divergent strategies), then hey maybe you're losing and that's not good either. And if they're buying Provinces, congrats! You have an entirely dead card in your hands!
There are some situations where I'll buy Smugglers: it's my opinion that even the worst $3 cards are good buys about a quarter of the time, which is a much better ratio than any other cost level. Specifically it requires powerful, spammable $5 and $6 cards and opponents competent enough to go for them too: Minion and Grand Market (especially since it's so hard to buy outright) are my two clearest triggers for Smugglers. A lack of other +Buy also helps.
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Jester is an alright card, but I'm not sure it's quite as good as it looks. When I buy Jester, I generally expect that I *won't* be getting many good cards from my opponent, but am just as likely (if not moreso) to just keep handing them Copper instead. If I have the Actions to spare, or there aren't more powerful attacks, that'll be good enough to grab one: giving Copper isn't as destructive as giving Curse, but it's unwelcome all the same. Jester is better with heavy trashing, Potion cards, and deck inspection: that way you're more likely to get good cards yourself, or turn Jester into a Curse machine. It's way way worse if your opponent is buying lots of Silver.
Take this with a grain of salt, though. I'm not very good at playing Jester: my Effect With and Effect Without are both negative.