easy card finder ?

[OutlawZ]

You will find the cards on enemies when you defeat them. (Just like you find teeth, jewels, rings, etc)
There are also quests available from Black Mack in Tortuga, that reward you with cheat cards.
[Correction! - Black mack can be found in the Rowdy Rooster tavern in Port Royal]

I don't know if certain enemies have cards.
As you play the game, you "win" things with some "kills",
treasures and items, trinkets and playing cards.

The playing cards don't come that often and some times you don't even notice what you have found, because you are focused on a mission or another battle.

You can't even look at the cards you have!
Only way to see your cards, is sit down at the Poker table and enter the "switch card" procedures.

If someone was to log every treasure, as it was found, right from the beginning of the game, then you might find a place to get cards, but I don't know of anyone who has done that yet!

I know that I have gotten cards from "undead" in all areas of the game. I am not sure that I have ever found a card on a Soldier or EITC character (but I could be wrong).