I don't get the cards thing.
Here's a post I made at toucharcade about the cards
The card rules are as follows:
-If you successfully take over at least one territory in a turn, you get a card
-There are 4 card types: army, tank, airplane, wildcard
-3 of the same type gets you a bonus army
- a set of each type, army, tank, airplane gets a bonus army
-wildcards can count as any (hence the name)
-the option to cash in your cards for bonus army shows up when you have one of the combos above.
-you can tap on the cards to chane which ones you want to cash if you have more than one valid set
-you can decline to cash in your cards if you have 4 or less (save them for later)
-you must cash in your cards if you have 5 or more
-wipe out an enemy entirely and you get his cards (this is damn useful anc can make or break a game)
-if you wipe out an enemy and have 5 or more cards you cash them in immediately and get to keep playing/destroying
Each time someone/anyone gets a bonus army, the size of the next bonus army anyone can get increases. In long games it gets crazy big, dont let it go that long!
Also, each card represents a region (they actually appear over the region they represent when you view the cards). If you own that region you get a couple bonus armies to that area when you cash in the cards (usually not a big deal, but nice).