Ok so based on the FAQ I've gathered a couple things. Theres 2 types of currency, Gran, which you must either spend real money to buy or get through special events (or recycling old cards), and Fight Money, which you get from just playing the game. Both currencies will be used to purchase things, and in many (though I'm not sure if it will apply to all) cases items will have both a Gran and a Fight Money price. From what I understand purchasable items will include Packs from released sets, avatars, items for your avatars, and pets for your avatars.
So does that cover everything that will be sold? Theres no auction house for players to sell individual cards but will individual cards every be sold by the computer? Will everything have both a Gran and Fight Money price or will some things been Gran or Fight Money only? Will there ever be promotional cards that aren't available in packs and if so will they be purchasable from the games shop or will this be a case where because theres no trade system if you missed the event to get them the cards are forever unavailable to you?

