Here there are two forms of currency. There are Galleons, (Gold Coins Which are broken up into other denominations, but always listed on your sheet as a Galleon sum, so you could have a decimal. IE: 40.49 Galleons.) And there are also dollars, (Real world money that as well can be broken into a decimal.)
Where you spend these currencies depends greatly on what you are trying to buy. All magical tools, implements and ingredients will be purchased somewhere in Vayle (Usually Arlane) and you will use galleons to do so. All real world tools, implements and ingredients will be bought with dollars.
Why are we keeping track of both currencies in this game? That is because not every character controlled by a player is a magical student, there for they need to also be able to keep up with wizards and warlocks while involved with anything dangerous. The tools and implements that you get from the real world focus' on improving one's "Stat" bonus, while the tools and implements that you buy from the magical world focus on improving one's "magic" bonus.
There will be a list of objects and their prices, as well as some form of conversion here.