When you receive Tess, train her until you get the spell Feeble I or II, and Feebos. Once you have received these spells, they will be very helpful against tough enemies and Bosses. When fighting a Boss that does a lot of damage and you want to weather it, use Tess or Deliza's spell to weaken their attack greatly. For a single Boss, use Feeble II. For tough enemies, use Feebos.
Defeating Dread Knight
Use Tess's Feeble II spell to greatly reduce the Dread Knight's high attack power. Keep Felis in case you need to use an item or heal with Restoras. Attack the Dread Knight with constant attacks from Lance and Goken. If you want to prepare to use a Group Lunability, when you are steadily reaching 500 make Deliza and Tess ready for a Group Lunabilty ahead of time. Use Deliza's Last Wind Lunability as it does the most damage.
Defeating the Dark Lord
When fighting the Dark Lord, make sure your heroes are at least level 65. If your heroes are below level 75 and you have trouble gathering for Pyrostorm, instead use a lot of Razor Spins by Lance and Feet of Fury by Goken. For Felis, keep using the Restoras Spell, even if the Dark Lord has not attacked yet or your heroes are at full health, because the spell takes some time. When the Dark Lord attacks, the spell should be finished by then and you will have your heroes healed immediately after he attacks. Keep doing multiple attacks from Lance and Goken. If you are above level 75, prime up the Lunar Gauge with multiple attacks from Lance and Goken. Keep Felis prepared in case something happens. Keep attacking until you are above 700 Lunar Gauge. If the Dark Lord tries to cast a spell, instead of using regular attacks have Lance do Razor Spin or Goken's Feet of Fury. The Dark Lord will eventually die after repeated sessions of spells. Note: If you are below level 70, things may vary. Make sure Lance is equipped with the Elemental Sword (Fire) before going into battle.
Easy money
At around level 10 after Gozen joins your group and you defeat the Demon Wolf, go to the crafting store in the Jade City. Buy Hardbone Hilts and Steel Blades and make some Sabers. You do not need the recipe, as the ingredients are as mentioned. Combine the Hardbone Hilts (150 gold) with the Steel Blades (300 gold). The created Saber can be sold for 1,000 gold, giving your a 550 gold profit. If you do it on a large scale, you can make a large amount of gold quickly. Save the game often, because if it fails to craft, you will only lose the cheaper Hardbone Hilt. Also, once you make one Saber, the recipe will automatically be added so you do not have to keep selecting the ingredients.
After defeating the Morzad King, use the Lighbra Gate to teleport to Jade. Go to Market Plaza and talk to Mahatma (near the entrance to Port). Accept his mission to deliver supplies to either Rem Village or Domerune Port. Talk to the clients at the location you chose and you will get an easy 2,000 gold. Repeat this as many times as desired.
Extra damage
When using a Group Lunability, there will be a circle expanding and a circle expanding inside of it. When that inner circle is about to become the outer circle, just before it becomes a full circle press X and your Group Lunabilities will do much more damage.
Quicker travel
When your using Lighbra's gate to travel around, it greatly reduces travel time, but at the cost of much needed monster encounters.