Gold

Gold is actually useful as a trade medium. People just need to get comfortable with it.  It's not wholly necessary for the devs to create a merchant NPC to accept it (though it might be wise if they did).

If you wish to sell an item you've made, you can sell it for gold. If you wish to buy an item from someone else, you can buy it for gold. Sure items can be directly traded or given, but that requires mutual trust. If you're trading with a stranger, it's just as likely they can take what you give them and not return anything at all. You could easily get fleeced or scammed if you don't know the person you're bargaining with.

Gold however does not require trust. You simply put an item you're willing to trade up for sale at a price you think is reasonable, then people can either buy it for the price you've listed or not. And if you see an item for sale, you can choose to spend the gold you have and receive it or walk away. It's that simple.

So I very much encourage people to actually trade in gold, and have taken steps myself to place items available for sale in the center of town and ascribe value to the things I've picked up or created, so as to hopefully encourage others to do the same.

What I would encourage the developers to do is:

1.  Create an NPC that accepts gold in exchange for certain goods.  This can help establish a value baseline for ingredients, crafted items, etc. in gold, and might have the added benefit of helping those who've lost tools regain them again without having to construct them themselves.
2.  Watch carefully the amount of gold that can be gotten through mobs, quests, etc.  If gold is to be a value medium in this MMO, then inflation/deflation is a very real thing.  Too much or too little of a currency could prove detrimental to trade.