There are quite a few vendor recipes in Path of Exile and some are more useful than others. Most are in fact not worth using consistently but there are a few that are easy to use and produce more valuable poe currency. Below is a basic list of vendor recipes you should be using to increase your wealth.
1. Quality gems for Gemcutter’s Prism: you know all those spammers who are constantly buying low-quality gems for 1 Alchemy? If you vendor multiple gems with a combined quality of 40% you’ll get back a Gemcutter’s Prism. If you do some simple math with the currency trading ratios you’ll notice that one GCP is worth about 15 Alchemy, so buying 8 gems with 5% +quality each would nearly double your investment.
2. Chromatic Orbs: it’s possibly the easiest of recipes: you simply vendor an item (of any rarity) with 3 linked gem sockets of different colors (RGB) and you’ll get a Chromatic Orb. While it’s definitely not the fastest way to riches in PoE you will constantly find them while leveling and farming. Many players don’t even bother picking these items up so be on the lookout for them while farming in groups.
3. Chaos Orbs: there are three Chaos Orb recipes. Both require you to sell a full set of rare (yellow) items: 2H Weapon (or 1H and Shield), Head, Gloves, Boots, Chest, Belt, Amulet, and two Rings. If all poe items have +20% quality you get back 2 Chaos Orbs, and you get 1 if you sell them without +quality. Since finding rare items with decent +quality is fairly rare I usually just use the non-quality recipe. Finding Armourer’s Scraps isn’t too difficult as well but you will burn through your stacks very quickly if you keep using them for the recipes.
Don’t waste your time. As I said at the beginning there are tons of vendor recipes but most of them are just a waste of time. If you want to maximize your farming time and income I suggest sticking with the three main recipes I mentioned above and ignore everything else. Picking up random + quality items or flasks and selling them for Armorer’s Scraps/Blacksmith’s Whetstones/Glassblower’s Baubles is basically a waste of inventory space and time. They are nearly worthless and if you miraculously end up needing that currency it’s extremely inexpensive to purchase.