I had some pretty stellar RNG in the early game and made very few mistakes up until the very end of the game.

I recently discovered a glitch with the Resurrection spell with czaj and SepticTank5 in that whenever a character dies while in slot 2 or 4 in the party lineup, they're Strength, Hits and Offense get doubled (to a max of 50k) until the fight ends. This saves several turns at Black Dragon as it's faster to attack until you die twice than it is to cast Weaken 12 times and then start fighting.

My biggest mistake (Cost 1:25!) was forgetting to reequip the Holy Staff to Elrad before I spoke to the king heading to Blood Island. This caused me to not have enough MP to finish the Leviathan fight quickly.

I also made a small mistake putting Hero in the 2nd slot instead of the 4th. Having Hero in the 4th slot allows him to get to Black Dragon and start attacking immediately. I lost a turn trying to move into melee with him. It wasn't the biggest deal ever as my offense was so low I couldn't hurt him anyway, but it could've helped me die a bit faster to get things rolling. There's always next time! :)

Note about the glitch:

1. It does NOT affect damage coming from spells, as seen here, as spells have a flat range of damage they deal.
2. The buffed stats only last for that specific battle.
3. CONSUMING AN ITEM BREAKS THE GLITCH. This is why I kept Astina alive as long as I did -- Her spells heal without consuming anything like an Elixir would. Cure Rings CAN work, but they have the potential of breaking each use. The Rune Helm is a decent alternative, but it only heals 1k HP at a time, where Astina fully heals.