Orb of Fusing is one of the most commonly used Currency items in Path of Exile. It is used to create links between Sockets, hence making it a critical consumable for players on all levels. Links can be created on Items like Armors, Helmets, Gloves, Weapons, Shields, Quivers (only Unique ones), and Boots. Since only linked Sockets will inherit properties from Support Gems, properly linked items are necessary to reach higher levels in PoE and face harder Bosses. It is still unclear what is the exact number of Orbs of Fusing required to reach all specific combinations, but it's been evaluated that you will need an average of 1,000 Orbs of Fusing to obtain six links on a 20% Quality item. Each percentage of Quality increases the success chance of Orb of Fusing by 1%. Since you can get up to 48% Quality on Rare items by using Perfect Fossils and Crafting Bench, it's common practice to upgrade an item that way first, then six-link it saving a lot of Fusings. After you have reached the desired number of links you will then remove all attributes by using Orb of Scouring and proceed to craft the Item that you were initially seeking.
It is also possible to use Vorici's recipes to have a guaranteed number of links on your Item. Two links will cost one Orb of Fusings, three will cost three, four will cost five, five links cost 150 Orb of Fusings, and the guaranteed sixth link costs 1500 Orb of Fusings. Obviously, if you are planning on creating your links on a high-Quality Item, it's a much better option to just use Orbs of Fusings directly. The interesting part about this recipe though, is that you can alter Corrupted Items using this recipe, however, for each Orb of Fusing required in the recipe, you will also need to spend one Vaal Orb.
Orb of Fusing can be commonly found by players throughout the storyline and a lot of them drop in Maps. However, because of how many of them are required to six-link Items, you will often find yourself missing a lot of them, and in need to exchange some of your other Orbs to reach the number of links that you need. There is however quite an easy way to obtain them quickly when you reach Maps. You should always pick up items with six random sockets, as vendoring them will always give you 7 Jeweller's Orbs. Then, you can buy Orbs of Fusings directly from any Currency/Flask vendor in the game, which costs exactly 4 Jeweller's Orbs. So basically, each six socketed Item will give you nearly 2 Orbs of Fusing every time. You can also buy Orb of Fusing with real money on Odealo Market. Multiple sellers offer their Orbs including Orbs of Fusing on our Marketplace, where you can expect their Orbs to be always in Stock, and offered at the best price available. Odealo is one of the best websites to Buy and Sell Orbs of Fusing with real money. At the same time, all PoE Orbs of Fusing on sale here are listed by other Path of Exile players, making it the most secure place to buy them. On Odealo you can pay with real money to buy Orbs of Fusing on all platforms including PC, Xbox One, and PS4 with full support for Permanent and Temporary Leagues like Blight and Metamorph Temporary Leagues.