World of Warcraft Item Upgrades
Upgrades to an item are a way to increase the stats of an item. Depending on the type of upgrade, it can increase an item's Rarity or Mark Level and increase other stats.
Each item comes with a track for upgrading it. Each upgrade increases the cost of the following one by a set amount.
Item Level
The value of an item's base stats increases as it is upgraded. The value is the sum of all of its leveled up advantages (attack, magic attack and defense). The cost of upgrading items can be high, dependent on the upgrader and the type of upgrade you choose to do. This is due to the variety of perks that need to be changed in order to upgrade an item.
It is also used to enforce gating requirements when queueing for raids, dungeons and scenarios. It is also used to limit the amount of PvP gear players can wear, since PvP is limited at a lower level. Players can see their average level of item on their character sheet.
The level of an item can help players evaluate the power of equipment when they decide to buy or sell. It's a sign of the item's damage and its quality. The level of the item can be used to compare items when evaluating the inventory of a seller.
The level of the item can be viewed by pressing the ALT key on a PC or using the left stick (L3) on XB1 and PS4. This will show the item's full description, including ilvl. It is also accessible by hovering an item with the mouse cursor, and then typing /itemlevel into chat.
There are several theories about how the level of an item is calculated. One theory is that the item level is a number derived from a formula that determines the amount an item's stats are worth. It takes into consideration the fact that different perks have different worth, and also that sockets have gems that increase the overall value of the item. This process could result in a calculated value for the item's level, which is typically close to Blizzard's real item level.
It's not the only thing that affects the value of an item. The degree of the area in which the item dropped can also alter its stats. For instance it can increase the item's haste, or crit rating. This means that items dropped at higher levels will have more value than items dropped in lower-level instances.
Item Stats
Item stats can make or break an item for players. The game makes use of them in various ways to encourage players to not restrict themselves to a particular weapon and to motivate players to experiment with other weapons. The base stats on a weapon are enhanced by the weapon's stat modifications that are in turn boosted by the player's level.
Upgrades to the item add by increasing certain stats of the item. The costs for upgrades are determined by the rarity of the item. A white or grey item, for example, will only be upgraded one time, while an item that has rare tiers can be upgraded multiple times with higher costs.
Affixes are another way to change an item's stats. They are stat boosts which can be added by the player to an item. The affixes can do things like give the item additional damage, add a special capability to the item (such as reviving dead or cutting down the duration of cooldowns) or make the item unique by giving a special name to the item.
All affixes can be currently re-rolled by selecting them in the upgrade window and pressing the green button. This procedure will cost the player a certain amount of gold as well as items which can be added to the upgrade gauge in the same manner as other rerolling options.
Players can choose to upgrade an item by a specific stat or reroll the affixes. The range of stats determined by the item's level. However, all items will have at least one stat in the same range, unless it's an item that is unique or the item is a God Roll from a boss in a raid.

Another thing that could be changed by adding an option to upgrade the equipment without having to reroll the affixes, or selecting which stats to increase. Like the base equipment, this will have to be done per item, and the item comparison interface wouldn't display all possible stats simultaneously.
Item Luck
The Luck stat of a player boosts the probability of obtaining items as well as the properties created by loot and the strength of these properties. However, it doesn't directly affect damage or the ability to upgrade items. It merely gives the player a chance to upgrade their gear in earlier waves, and is therefore more beneficial in early game runs than in later ones, as most players prioritize higher weapon scaling and defenses over raw damage gains.
In addition to influencing item discovery, Luck also increases the chances of success when upgrading items with the Blacksmith. This is not to be confused with the Blacksmith's overall chance of upgrading that increases with each level and can be further increased by using an anti-material such as a Scroll of Strength or a Jewel of Blessing.
The shields, armor and weapons have a default Luck value of 40. These items can be enhanced with golden ingots, or spined leather (depending on their material type) to increase the value of 40 luck or to increase an item's existing Luck up to 140.
Moreover some items, like the Hollow weapon that is infused with hollow can be used to increase the damage of any damage-dealing skill by 5%. These items can be purchased in the shop or made using the correct ingredients.
Item Failure
Not all upgrades work. However, there are some cash shop items that allow players to boost their chance of success or stop themselves from losing an item if the upgrade fails.
When you upgrade an item the success rate is displayed in the Honing UI. The percentage represents the probability of completing the upgrade successfully and can be increased by adding Additional Materials or Special Materials. There are item upgrader to the extent to which the success rates can be improved and the probability of a failed upgrade cannot be greater than 100%..
The performance of an upgrade is also affected by the Luck of that item. All items have an average success rate of 25%, and every item that has Luck increases the chance of success by an additional five percent.
Note that upgrades to items are rendered above the inventory items, so enchantment glint and other effects can be obstructed by the overlays. If you wish to disable the upgrade overlays, the config option decoration.renderUpgradeOverlays can be set to False in the Item Upgrader CORE client config.