Best way to spend Allagan Tomestones Of Poetics since Stormblood

This Youtube video shows you how to use the Fantasia Potion. There are a few things which you have to do before you can use it, for example taking off all your gear.

1.) Yes, you will be able to change your race, gender, etc the next time you will login. The Fantasia Potion gives you the chance to change everything except your starting class.

2.) Additional Fantasia potions can only be purchased in the Mog Station for real money.

Okay so, in order:

Matching Requirements: Duty Complete means people need to have completed the duty before to be matched. Incomplete means anyone can be matched (I believe).

Purpose: Practice is for learning the fight, Duty Completion is for actual attempts to clear it.

I'm not sure which purpose is quicker, but Duty Incomplete definitely is the faster matching requirements - there's a lot more people wanting to learn the fight than there are people who have already completed it.