The immediate problem is that you'd be forcing yourself to hand out to commoners items of magical powers. I don't know if you want that to be the case, but as Lord Such-and-Such I don't think I'd like to be handing out rare magical gemstones to Jimbo the Fishmonger.
It might be easier to create a two-tier currency, where these magical coins are used for the top-level transactions.
Also realise that you're now potentially setting up a world-level economy, which we don't even have now in the modern age(we just have a "we'll accept it everywhere" currency of USD, but how long that may last is debatable).