You receive a vision of a rooftop "somewhere close by", where a rare moss grows; in the vision, you know the moss is suitable for greatly enhancing the effects of certain types of potions. Now go and find that rooftop. Don't fall off. (Of course, rooftop runners *will* be taken for miscreants by the local City Watch....)
Tarot Cards are used by Magic folks to predict the future (cartomancy). Since the present becomes the future through the interplay of elementally alligned forces, the tumble of cards can give clues to the way the pattern of elements will be in the future.
This means a wizard will have a deck of cards with them. Since cards were used to train wizards in legerdemain, Since they have cards with them, they frequently know how to use them. Guild magic users often have a knack for fancy shuffles, palming cards, and a variety of card tricks and games.