Patch 10.1's gear system is a big overhaul and has been quite intimidating for many players, so in this week's GG WoW video, Dratnos and Tettles break down the new system and what you need to know! Read more about the upgrade system in our guide. The basics of the system are VERY forgiving and it will be hard to make serious mistakes with it due to the upgrade discount system that kicks in once you have higher item levels in that slot already.
Whatever level of content you do, you'll be able to make use of the system to improve your gear, and especially for Normal and Heroic raiders there's much higher caps on what you can bring your gear to. There is a few cases, however, where high end players may accidentally end up delaying their potential by a few weeks, which Dratnos breaks down as follows: if you are a player who will be doing high keys (17+, ideally 19+) in the first few weeks, and/or a Mythic raider, try not to upgrade from 424 to 431 using crests — upgrading below or above this band is generally fine but within this band is inefficient if you're doing M+ keys that can drop the 431s.
Whatever type of player you are, try to focus your upgrades on the high budget slots like weapons, chestpieces, shoulders, and legs. Also, try not to craft Enchanted Wyrm's Crests and instead focus on using your Wyrm's Crests for upgrades — make Enchanted Aspect's Crests instead (or, if you'll never get those, only make the Enchanted Wyrm's Crests after you're done making big upgrades with the unenchanted ones!) For some more info, check out Dratnos' spreadsheet and his video.
. Read more on wowhead.com