This achievement requires a few things
First is the upgrades from leveling up to even be required to make the items named Craftsmanship. It can be unlocked after buying two upgrades in the Industry category (Industry -> Either Carpentry or Sewing -> Craftsmanship) I recommend aiming for a few more upgrades you think are more useful first but this will come quickly for some quests and tool upgrades.
Next, you can choose between either the steel or clothing. Both you'll eventually make a lot of, just whatever comes first.
Both of these materials require one of each of the gems: Ruby, Topaz, Amethyst and Emerald. Royal clothing is made at a sewing station and needs the gems as well as 2 leather (made from hide [from animals] and thread and needs the sewing upgrade mentioned previously) and 4 thread (made from fiber, which the foraging upgrade can help finding more of). Royal steel is in my opinion the easier of the two to get. Aside from the gems, the royal steel requires 1 normal steel (from 1 gold, iron and coal each which you should have plenty of) and 4 coal.
Once you make the item, the achievement will pop!