Gearing at Endgame
There are 4 ways to gear up your WHM, depending on which 2 of the 3 stats that you want to focus on (Determination, Crit and Spellspeed), you will gear up accordingly. I recommend spending your first 900 Myth on +1 your relic weapon, Thyrus.
As for which stats you want to focus on, there are 2 vocal camps (Det/Crit vs Spell/Crit) but frankly a lot lies in your luck in Coil. If you been getting a lot of healer loots, then you have more options to decide on how to spend your Mythology. Personally for me I am gearing Determination/Crit, but eventually I would like to also have a Spell/Crit set.
Remember that for Rings you can only equip one of each types. You cannot wear 2 AF2 or Allagan rings. So spending your Myth on a ring is guaranteed no wastage/overlap.
In the process of gearing up, if you have to replace your DL armor with an AF2/AG armor, you should always use the WP headgear over than AK headgear. The 14 Crit and 7 Determination is a no brainer over AK’s 9 Piety and 11 Spellspeed. You only lose 2 Vit and 1 Piety, which is negligible compared to what you are getting from wearing the WP headgear!