You should be able to sell cards for a small amount of coins, or maybe trade them in with some coins for a card you prefer. I use this mostly as an idle game, so I don't get a lot of use out of Tukkun FCG and the button machine (and quite frankly, I probably wouldn't use the button machine anyways :P).
Flygon, there's a Kongregate chatroom for Anti-Idle the game, multiple in fact. Small questions like that can be asked there, there are a lot of knowledgeable people there. To answer your question, you get an achievement.
There should be some quest prerequisits. For example, I haven't even gotten the achievement for completing one, but I got a quest to win THREE impossible simple races (lol oxymorons). That shouldn't happen.
While holding shift on the button machine can be good for getting lots of coins, exp and some achievements, keep in mind that your multiplier is halved.
Spectre: Buy boosts, upgrade your progress bar in the shop and/or turn idle mode off. That makes it go faster (but if you turn that off you need to jiggle the mouse or do something to reset it)
 "Anti-Idle: The Game"){kind=icon}
 "Rebuild 2"){kind=icon}
 "A Knight's Story 2"){kind=icon}
 "Learn to Fly 2"){kind=icon}
 "Hands of War 2"){kind=icon}
 "Get Off My Lawn"){kind=icon}
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