Quote Originally Posted by Urthdigger View Post
Also, when it comes to main stats like int it's important to take into account stat caps. Every piece of armor has a maximum for each stat based on it's ilvl and slot. For HQ crafted gear, dungeon drops, and tomestone gear, most of the stats on there are at or near their cap, which means you won't be able to meld more intelligence. This also means you may need to meld the second-most important substat, such as melding crit onto BLM gear that is already capped on spellspeed.
As of a couple patches ago, the melding window now shows all the relevant stat caps along with the gear's current values, so when planning to meld something, start by bringing up that window and selecting the gear, as though you were ready to meld something onto it. Then you can check the numbers at the bottom of the window to first see what you're able to meld. Do that before deciding what you want and collecting the materia for it.

As mentioned, your primary stat is likely to already be capped from the gear's initial stat boosts, in which case you can't meld any more. But if you have a piece where you can add more of your primary, go for it. The most common case for that is tanks, who have Vit as their real primary stat, but Str adds just as much to their damage (making it sort of like a pseudo-primary stat), so they'll sometimes get Vit jewelry and meld Str to it or vice-versa.

In some cases, it's possible to make NQ gear end up as good as HQ gear by melding more materia to it, though I'm not sure if that ever occurs with combat gear. (I know it can with certain DoH / DoL gear, but those only have three relevant stats to deal with, so the gear is maxed if you can get all three to their stat caps.) With combat gear, there are more relevant stats, so you'd likely end up having to give up a secondary stat meld in order to finish maxing out your primary with materia on NQ gear. (I'm not sure how useful that would ever be.)