At the moment, only gems are shown in the merchant, although different items can be purchased with a number of "currencies" eg. star coins, beans, stalks, guild coins... possibly more, can't think of them off the top of my head ;)
It would be useful to have all these currencies listed at the top, so we can see if we have enough for, say 2 of this and 1 of that without having to go and look in the mayor's house or wherever.
