You are allowed to collect one card pack per day, this being monitored by scanning your entry ticket. You are not allowed to just go and collect the cards! You HAVE to play the game at least once every few days otherwise your access to the game will be blocked and you have to go plead your case back at the Engine Co. 71 base.
As you progress through the game, you become more powerful and things get more interesting.
Definitely very fun to play!