Most equipment falls into the following requirements

) Can only be equipped buy a single main class, or job.
2) For most classes there is a set of equipment choices available to upgrade to every 5 to 10 levels.
3) For most jobs, the levels you can upgrade basic equipment at is 10, 20, 30 and so on. The Mage job class's equipment level most of the time starts at 8, 18, 28, and so on.
4) All equipment has a set number of upgrades available. To upgrade, you need scrolls. This will be explained in a later article.
5) Each new set of equipment available at each "upgrade level" usually has a few bonuses above the previous set available.
6) Each set also usually has a variety of choices in colours.
7) Each colour has set average bonuses the particular piece of equipment can have and usually pertains to the desired stats that the class would use.
8) Most equipment that are considered accessories (rings, earrings, belts, etc) are not job dependent.
9) There are occasional permanent and temporary equipment from events and quests that do not always follow this list. For example, the maple anniversary weapons that fall on levels 35, 43, and 64 for their respective upgrade opportunities instead of the usual 10, 20, 30 pattern.

Some of the equipment are common, meaning any class can equip them, and available to be equipped by 2 or 3 classes. This allows players to upgrade some equipment in ways that can be used by multiple job classes. When these items are upgraded to the point they are considered good or "godly" their potential selling price to other players can be very high.