Tear Gas Vial is extremely useful as using it (along with damage buffing items noted below) gives you the possibility of killing a few enemies in one turn, minimizing the damage you take later. DumDum Bullets / Grindstone are good for additional damage. A character (or 2) with a Healing Adrenaline Rush IS A MUST, especially for later Story Missions or Roadmap Missions. Healing items (Replenish, First Aid Kit, Energy Burst, High Replenish, First Aid Case, Deluxe Replenish) ARE A MUST, especially for later Story Missions or Roadmap Missions.