Basically everything mentioned here is correct, but your journey goes as you go, as in finding the runestones(first runestone Eikthyr is at first spawn, they all look the same but in different areas as mentioned above) tells you where next boss is and you mine and search for the objects to summon the bosses one at a time to unlock more materials to upgrade everything including building materials. Now the Trader is in different locations but only first one you get close to will be your only Trader, Take A Portal, as a mater of fact,

TAKE A PORTAL EVERYWHERE YOU GO!
Sorry but cant express enough. If in doubt put a portal down, mark on your map if need be.