As the achievement description describes, there are 64 baseball cards in the game. Here are some useful tips when going for the achievement.
-At the start of the game, you will have 8 or so cards initially unlocked. These are "Actions" and a couple of "Multiplayer" cards.
-Cards cost coinage to purchase, but many also need certain requirements to be met before you can buy them. For some you need to beat certain levels, and for others you need to purchase certain cards first.
-This is the most important, there are two cards under "Score" category that increase your coin payout. There is a $1000 card to get 1.5x multiplier, and a $2000 card that gives you a 2x multiplier. These aren't available until you are nearly done with all the levels, so try to avoid spending money on anything if you can help it so you can buy these as soon as they become available. The exception should probably be the fatigue cards as they become available.
-You may be tempted tempted to buy up all the lower priced cards. It is much more productive if you save money up for useful cards that will directly help your gameplay (and in turn, increase coin production). First get the coin multipliers (see above). For Diabolical pitches, I wouldn't buy anything other than the Lightning Pitch and it's power ups (when they become available). The normal ball damage improvements and the lock-on damage improvements are also good.
-The Multiplayer cards won't all become available until you play through the multiplayer campaign, so this achievement won't be possible in single player alone.
-Since this achievement takes a long time, you should play for the "Something to Brag About?" achievement (I have a solution for this) as you are collecting coins. Obviously, the more powerup cards you have, the easier it becomes (which is why it is important not to buy anything you don't need until the end).
-If you just want to get some quick, easy coinage, I found that the extra stage on the Space World is quickest. With the multipliers, you can get 250 coins a go, and it only takes a couple of minutes.