Higher Dexterity = Higher chances to dodge an enemy's attack.
You get Dexterity Excelia by successfully dodging an enemy's attack, if you eat at the Hostess of Fertility before heading to the Dungeon, your excelia's quality will increase a bit (you'll gain more), but the best quality is from a stronger enemy than you, so dodging goblin's attacks as a level two wouldn't give you as much Excelia.
The game is currently mostly complete (99%), I am developing the last release (R36) before calling it complete, as there is a lot of stuff to refine and fix before I am happy with calling this game complete, you can follow the progress here: https://pastebin.com/tanaPpZF
The game currently covers the first 8 volumes, the sequel will cover the rest but it'll be a different genre. You can read more about it here: https://www.patreon.com/posts/future-of-legacy-76603389
Once this game is completed, I'll make a public poll where people can vote what game they'd like to see next, one of the choices will include a sequel to this game.
This is the link to my Discord Server: https://discord.gg/usyhE2k