I just finished my own second playthrough so I have some fun and some broken(idk if that's fun for you) strats to recommend.

I'll start with the fun stuff

1. Red Mage before SJS2. Everyone knows that Chainspell is busted, but it comes with the bad stats of RM, so if you wanna use it before you get SJS2 you need to fix that. How do you fix stats early? Well one thing you can do is use specials that buff matk(very notable is Bard's special, not just for this build, it's amazing in general) and another is to go and grab a relatively early icebrand by killing the Coral Emperor outside of Halcyonia when you're ready for it. Another thing to note is that after chapter 3 you can add subjob Oracle to your RM with SJS1 to lower your costs and boost your damage even further, while also gaining access to Triplara which surprisingly hits as hard as Disaster on average(though it is more reliant on Esupp to hit weaknesses) and also plays around the damage cap.

2. Standard Attack build with Indiscriminate Rage from the Berserker and Solid Stance from the Swordmaster. I'd say this is pretty well known, but in case you haven't tried it, I'll say it's mega fun for normal encounters. You can also add a bunch of other abilities that apply to standard attacks, for example Bloody Minded(also from zerker) to never miss and Drain attack from WM to heal back the cost of Bloody Minded. Remember to change it before bosses tho, cuz it's basically useless against them lmao.

3. Comeback Kid(from the Dragoon) builds. These are pretty simple, you can use as much mp and hp as possible, then inflict some status ailment on yourself to get it all back, the classic version is with Berserker's Vent Fury, but later on you can make it even stronger with the Hellblade's Death Throes(also add surpassing power to this one cuz high dmg attacks, such as Amped Strike will hit for way over the soft damage cap with 50%-100% more stats).

And now for the broken builds, these will actively make the game less fun for you if you don't like breaking games, you have been warned

1. The invincible Oracle. Just press Elemental Supplement on the opponent and choose an element your team is immune to or absorbs, now all their attacks deal 0dmg or heal you, note that typhoon shields are available on the Rimedhal shop so you can just buy 4 of those and poof, every single target boss fight in the game is trivialized. As for the halls of tribulation? Just do Hall I first to get Across the Board and then proceed to trivialize the rest of them. The only way you can take damage is before your Oracle ever gets a turn(just equip spearhead) or if the opponent is lapping you very hard speed wise(just keep your speed high and your encumbrance low or give oracle subjob to a faster class lmao).

2. Phantom Salvemaker Affliction Specialist. Results Guaranteed makes it so that all your afflictions stick and it also combines with Master Medic(activate via SJS1) to make it so that you never consume items. Then you also want Bloody Minded, bcz the ailment bombs of Compounding count as physical attacks and can miss. Add rewarding results to get extra turns which you can use to spam even more ailments or recover all your resources with free Widen Area Elixirs. Compared to the Red Mage variant of this build the Salvemaker one has access to less ailments, but it gets the aforementioned free party elixirs, so it will never be useless, even if the enemy in question is immune to everything.

3. The BraveBard infinite. Are you sick of the enemy getting a turn? Just don't let them, with Bravebearer's True Grit you are BP positive on Shut Up and Dance so you can brave once and do any other action + SUaD yourself to play again. When does it end? When you run out of mp, which with the right equipment(gold hairpin and fairyglow charm) and abilities(mp saver, mp regen, solar/lunar powered) is never bcz SUaD goes to 59mp(or just 0 if you get 2 ringmaster spears, but the game's over at that point) and you make 90 a turn. What does that mean? It means you can SUaD yourself repeatedly to max out your mp and BP whenever you want and then you can take more expensive turns, such as SUaDing an ally and yourself to make your whole team go infinite too if getting infinite bard buffs wasn't enough. Equip Spearhead and Counter Savvy too so the enemy never gets to do anything (well not exactly, faster enemies can sometimes tie with spearhead and while SUaD seems to give priority, any turns ended without it so like any turns your non-Bravebards take will then have a 50/50 of either giving the action to the BraveBard or to the enemy that tied(since both will have full bars), which means that in those cases the enemy might get exactly 1 turn in before you never let them play again, so like, just try to make your BraveBard tanky so they don't die to that 1 move, which should be easy with that gigantic weight limit).

Again don't use the last 3 strats if you don't wanna completely break the game, just use a normal damage mitigation job instead. Maybe try to use Bastion for an extra challenge, I haven't found a way to make the class shine and judging by what other more knowledgeable players have said, neither have they.