There are several hurdles to being adequately prepared for the most challenging content in Final Fantasy XIV. One of the most obvious aspects of a powerful Warriors of Light is their gear, but their short-lived tinctures give them the final push they need.
Tinctures are similar to potions in the sense that they're to be used in the heat of battle. Rather than restoring health or mana, these brews raise your character's stats, making you more efficient in the fight ahead. Tinctures, referred to as "pots", last 30 seconds and have a lengthy recast timer of five minutes, or four and a half minutes if the tincture is high-quality. Because of this, tinctures are often used during lengthy Savage-tier raids to give the party the extra push and ideally clear before triggering the timed Enrage.
While any tincture can be used by any of FFXIV's jobs, a tincture that increases strength wouldn't make sense for a job like White Mage. Try as they might, the mindful healer won't be able to swing their cane hard enough to make a difference with an increase in strength. Alongside their best-in-slot (BiS) gear, each job has a tincture best suited to them, raising the stats that directly affect their abilities.

Here are the best tinctures for every job in Final Fantasy XIV as of Patch 6.5:
Job | Best Tincture |
Paladin | Grade 8 Tincture of Strength |
Warrior | |
Dark Knight | |
Gunbreaker | |
Monk | |
Dragoon | |
Samurai | |
Reaper | |
White Mage | Grade 8 Tincture of Mind |
Scholar | |
Astrologian | |
Sage | |
Ninja | Grade 8 Tincture of Dexterity |
Bard | |
Machinist | |
Dancer | |
Black Mage | Grade 8 Tincture of Intelligence |
Summoner | |
Red Mage | |
Blue Mage | Grade 5 Tincture of Intelligence |
Alchemists are the key to obtaining high-level tinctures, as the Grade 8 versions are locked behind the Master Alchemist X recipe book. Having the Disciple of the Hand leveled to 90 or knowing someone else who's done so is the best way to ensure you're well-stocked for future battles. If all else fails, there's always the market board.