- Go for a physical build on the main character and magic for all the other characters. The protagonist can't use magic, but physical is pathetically weak until endgame so it's not worth doing it on anyone else if you can avoid it.
- The game hands out incense (stat boosting items) like candy, so it's easy to patch up weak stats. As a general rule: Strength and Luck incense goes to the main character, and Intelligence and Magic go to the Heroine. You can split Agility and Vitality equally.
- Don't use any incense on the Law and Chaos heroes, they're better suited for the main character and Heroine.
- Give the main character a bit of Intelligence, 10 will do but higher is okay. It plays into negotiations which can be really frustrating if you neglect it.
- As soon as you get ailment bullets, slap them on every party member. They make random encounters a joke.
- The Heroine's Zio line of spells can trivialize any boss. As long as you move first, you can shock them infinitely and make them unable to move.
- Keep a demon with Estoma on you at all times; in some dungeons the encounter rate is so high that it's every other step. The earliest Neutral demon that gets it is a midgame demon (Orthrus), the rest are Law aligned, so I recommend not leaning far into Chaos until then.
- Don't waste gems on items in Rag's Shop. You'll need them for Element demons which are needed to fuse the most powerful sword in the game, the Hinokagatsuchi. The earliest you can get it is level 40.
- If you want to minmax, stop giving the main character Strength at around 30. You'll get enough incense to boost it up to 40 and lategame swords/armor also give a little bit of additional Strength.