The short answer is to max your xp on the first stage enemies (2500 I think) and then avoid combat for the rest of the playthrough. Wizards have a variety of high-damage and insta-kill spells for tough enemies. Get Bows for your martial class characters asap.
Once your XP is maxed and your gold is maxed, go talk to the king and he’ll level you up to 5(you need the Mark of Kings to level higher) and pirate ships will appear on the world map. Fight one, take the ship, and sail it into a whirlpool to Ambrosia. Find the shrines and spend gold to max your stats, then find another whirlpool to go home. From there you can use any guide for dungeons and getting endgame gear.
SUPER IMPORTANT BUG: in Exodus’ Castle, ranged weapons DO NOT WORK. No bows, no slings, no daggers. It’s a bug. Count on kill spells and melee with Sun Swords if necessary.