Monsters drop items, cards and gears like normal (the rates for drops are 3 times as much as an official server in most cases). You have the option of donating/obtaining ad credit and buying items, gears and cards from the item shop (it's a lot easier to get rare/normal items, cards and gears this way but it's usually expensive.)
Edit: Although there are some items which are only available at the item shop, most you can get in-game.