My one game so far with Royal Blacksmith was an engine board with Amulet and Spice Merchant for trashing. That's basically the perfect board for it, really - you have fast copper trashing, +buy to pick it up, and you can gain a few Silvers for some economy for it to draw. Unfortunately, both my trashers missed the shuffle and I ended up a little while later buying the Blacksmith with four coppers still in my deck. This was a mistake, as it became difficult to get rid of those last few coppers. There was actually also an Embassy in the kingdom, which I should have bought before the Blacksmith.
So, in kingdoms with Copper trashing, you should still look to buy other draw before the Blacksmith to cycle back to trashers without discarding coppers, then go back and pick up Blacksmith to draw your deck. If there's also a powerful attack (particularly a junker), you might want to go Blacksmith early anyway so you can get back to it quickly (possibly not as good an idea with Mountebank, though).
Is this good without Copper trashing? I guess you could pre-emptively discard coppers with Warehouse, Royal Blacksmith to draw everything else, then a bunch of cantrips to get the coppers back. 4 Magpies is enough to draw all 7 coppers, that's probably the easiest thing, but Wishing Well could do work too. Maybe just a big engine with lots of cheap cantrips and a couple of Blacksmiths would do it.