Mainly your endgame armor depends on the innate traits you want, since even early game armors can reach same def/eva as most endgame armors, though it'll require more mats to upgrade. Sadly I don't play mage, so don't know much about it, but I'd assume a innate set with magic +1 or magic +2 would be ideal, then adding the correct Eidolons magicite to make it better. I'm just not sure what's good for mage stuff as I mainly been playing melee classes. But yea, basically in terms of armor, look at those with good traits you want, then upgrade them, this also applies to weapons as well. I'm using a Sword that I unlocked at 3 star at endgame, due to the fact it can be upgraded to reach same attack power as most endgame weapon, but it has a good innate trait making it worthwhile.
I'm uncertain on skills but I just see most use stuff like Flare, Meteor, Ultima, etc. I thought linking the spells would be pretty good with the lower tier, but guess not. I'd probably have to play it myself to see.
I think not a lot of people play BLM cause Sage is just so much superior I believe, compared to WHM as well. I personally wouldn't touch BLM either since Sage just looks so amazing. On top of that, Sage gets concentrate, which is probably the main thing that makes them so good. Sage is more squishier though, whereas BLM can take few more hits + barrier.
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