There is far easier way to duplicate things, at least in this game (doesn't work for the sequels), it doesn't involve quick loading and works with all items, not sure about if the dupes keep the stats (in case of weapons and armor).
This works best with potions, if you don't feel like a big cheater, but can be done with everything, including gold for getting some potions/armor/weapons "legitimately".
Open your inventory and a container (doesn't need a container, the ground works as good as anything, but containers are better for it), drag the item you want to be duplicated (works with stacks as well), keep the mouse button pressed, then pause the game (default "spacebar"), let go of the mouse button, you'll hear a drop sound, but the item is stuck to your cursor still, press escape to call the main menu and immediately press it again to resume (or press "resume", for the same effect), you'll see the item is gone from your inventory and isn't in the container either, now unpause with "spacebar" and they will appear, like in your inventory, so the copy in the container (or ground if you don't use containers). Keep doing this, till you have enough potions to keep you alive in big fights (or enough gold to buy everything).
