Trading Items in Path of Exile is an essential part of playing the game. Unlike many other games out there in Path of Exile there is no Auction House and no monetary system. What that means is if you need an item you are going to have to trade an item that you have for it. This system has it's ups and downs much like any other bartering type of system would. Sometimes you can get items for really cheap, sometimes it is a complete and utter nightmare to find an item that you need because not only will you have to find a player with the item but also have an item they want.
There are a few tips and tricks you should keep in mind when it comes to trading items between both players and to NPCs. Below this information I have a video that details a lot of these tips and tricks but I am also going to explain some of them here which will make watching the aforementioned video optional. In an attempt to make it easier for you to process all of this information I am going to break it all up into different segments.
When you vendor White items you will get Scroll of Wisdom Paper Scraps. 5 of these together will make a Scroll of Wisdom, which is at the bottom of the Currency Items food chain.
When you vendor Unidentified Blue Items you will get Shards of Transmutation back. These are less valuable than Shards of Alteration (about 1/4 as valuable).
When you vendor Identified blue items you will get Shards of Alteration back. These are better than what you would get from an NPC if you vendored an Unidentified Item.
When you vendor an Item with "% Increased Rarity of Items found" or a Weapon with "+ To a type of Gem in the Weapon" it will give you Shards of Alchemy back. If you combine 20 of these you will receive an Orb of Alchemy, one of the most valuable Currency Items in the game.
Now that you know all about trading items between players and NPCs there is some other extremely useful information that you may find handy. Below I have compiled a long list of Currency Items and what order you will have to trade them in to reach the top item, an Orb of Alchemy. You will need to vendor a hundred or so blue items in order to reach the Orb of Alchemy, vendoring Identified Blue Items will get you there faster than vendoring Unidentified Blue Items.
It will take an extremely long time, about 100 Portal Scrolls in trips to town in order to acquire all of the Orbs of Alteration you need to eventually reach the Orb of Alchemy. By the time you get enough Orbs of Alteration required you will have made three or four Orbs of Alchemy via the Shards of Alchemy that you find.
All of the below items can be purchased from the NPC in Act 3 on any difficulty. They are almost always available at this vendor but in other acts it is random if they are available for purchase at these vendors or not.
Tier 0 Currency Items Exchange
Scroll of Wisdom - Baseline Item
Portal Scroll - 3 Scrolls of Wisdom Each
Tier 1 Currency Items Exchange
Orb of Transmutation - 7 Portal Scrolls Each
Orb of Augmentation - 4 Orbs of Transmutation
Orb of Alteration - 4 Orbs of Augmentation
Tier 2 Currency Items Exchange
Jeweller's Orb - 2 Orbs of Alteration
Orb of Fusing - 4 Jeweller's Orbs
Orb of Chance - 1 Orb of Fusing
Tier 3 Currency Items Exchange
Orb of Scouring - 4 Orbs of Chance
Orb of Regret - 2 Orbs of Scouring
Orb of Alchemy - 1 Orb of Regret