- Don't buy new weapons for all characters, only the ones you intend to stick with for a while or know that you will have to play with for story reasons
- Gravity is pretty good up until mid game when monsters becomes immune to it
- Most regular enemies and bosses have status weaknesses which makes them way easier
- Damage Enemy Skills should be learned as soon as you can, as they quickly loses their strenght due to their base power. L5 Suicide is pretty decent throughout the game, as long as you bother with Sense or trial and error, and specially useful on end game optional bosses
- Defense and m. def. are way more important than in vanilla
- Earth is very important because most bosses and relevant enemies are weak to it, so always have 1 or 2 equipped to get Quake 2 or 3 ASAP
- Aeris is pretty good for conserving MP/Gil with her healing staves (until your characters gets 2k+ HP)
- Summons ignores defenses and are guaranteed to cause their specific status effect as long as the enemy isn't immune to it
- Items that gives buffs and debuffs can be really useful, and to a lesser extent damage items
- Berserk is insanely strong, maybe not on early game, though, so never forget about this option
Those are some pretty solid tips. I was surprised to see that the E.Skill Laser worked on Rude/Elena in the Mythril Mines.
Also, with Fort Condor, is it better to let the enemies overrun the hill and fight the Boss Monster, or should I participate in the minigame properly? I did a boss fight just then but I didn't appear to get any rewards for it.