The very first step in setting up your PVE crystals is understanding the spot where you are grinding.
To do this we use the following tools : -
Pve Hit Rate
PVE Ap caps

After you setup your gear on garmoth , you can check your hit rate and the AP cap of the spot on the links above. This will help us understand what mix of crystals we are required to run. Depending on the spot the crystal setup changes,

1. The Base

Critical damage is the most consistent and best performing special attack for pve. You should be aiming for as close to 100% critical rate build as possible to boost your PVE damage. Keeping this fact in mind,

a) Corrupted are the BIS crystals here. It gives you increased critical damage and some AP.
b) Dark Red Fang + Ancient spirit Valor - This combo gives you 5 critical Hit level (18% critical rate) and 10 ap. This means that you dont have to pop spirit perfumes or shock elixirs.
c) Glorious Ah;krad - Monster damage and increased attack/cast speed.
d) Rebellious Spirit Crystals - I include these in the base setup cause they give a good mix of stats. 5 AP + 5 Monster AP + 175 hp and 5% skill exp.

2. After your base setup is prepared you want to adjust the remaining slots depending on the need for that particular grind spots.

A) Monster AP 
If the only require for your grind spot is monster AP then for the rest of the spots you can fill the remaining slots with AMC-Crimson Flame-Power, these crystals give 5 hidden AP.

B) Accuracy requirement
If the spot requires accuracy then you need to check the PVE hit rate calculator to figure out how much accuracy you need to add. Start with adding Jin Vipers (1 or 2) and if its not enough then you follow up with Elkarr and the Hooms depening on the requirement of the spot.

C) Survival
If you meet all the AP/Accuracy requirements but feel a bit to squishy to grind some spots then this is the high HP/DR setup.

D) Other Notes
As you can see from the above examples you can mix and match the Base setup with the grind spot requirements to get the optimal setup.

i) Some spots like crypt require resist caps.
ii) If you are AP capped on a spot and do not require any extra stat like HP/Accuracy, then in that case you can use SPECIES damage crystals to give yourself a miniboost.
iii) The reason that the base crystals start from bottom is that the two wide slots on top are from having Garmoth's Heart on your awakening weapon. If you do not have this then these slots will be unavailable.
Import link for the base :-
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