Glumlee's part of the Main Questline can actually be done before the game asks you to, making this an easy achievement. Just go into the portal on the left side of the main hub, then talk to Glumlee (the glum looking goblin. To talk to him you gotta click on him.)
He'll first ask you to mine 5 copper ore, just click on one of the piles of ore and wait (or play the minigame, it can speed things up a bit). Then he'll ask you to smelt one copper bar - click on the forge and place the copper ore in, and you can speed it up with the oil barrel Glumlee gave you. Finally, he'll ask you to buy three forge upgrades - you need money from other quests and from killing monsters for this one, though if you're doing this at the point the game asked you to you'll likely have the necessary money.
Once you've bought those forge upgrades, you've finished Glumlee's part of the main questline, and should have the achievement!