Market browsing is most dangerous right after a failed dungeon run. You know you want more power; you do not yet know which stat or item is holding you back. Write down the next content gate first. Then compare listings only for upgrades that address that gate.
Check the whole cost
The sticker price may not be the final price of an upgrade. Include enhancement materials, transfer needs, and anything you might have to replace soon. If a cheaper item becomes unusable as soon as your next dungeon unlocks, it may be the more expensive choice. Check whether the listing uses regular Kina; NC's regular/bound currency split matters here.
Leave yourself an exit
Watch more than one listing and, if possible, more than one session of prices. Limited events and patch changes can shift supply quickly. Do not empty your balance to match a build made for another region or season. If you cannot explain why this item helps your current character, close the market and do a run you already know. That is usually a better way to learn what you actually need.