What to spend crystals on after energy refreshes?

Edit: my 1st comment had gone into approval.
I rewrote it.

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In my opinion...

Your crystals just sit there doing nothing.
It is best to spend it on gears (not gears from the store...they are scams! But gears on the shipments).

Just build your characters little by little by buying gears from time to time.
Characters that are built little by little will serve you better than sitting amount of crystals.

They can strenghten your fleet so you can climb or at least preserve your fleet rank...if you are at rank-above-rank-50, it means you get daily crystals. With that daily crystals, you can buy more gears and so on and so forth...

They can survive better in GAC. Survive better in GAC = could mean a promotion to a better league = better daily crystal. Not to mention the GAC winning rewards.

That is how i play...
I never keep too much tokens (various currencies with which you can buy something from the respective shipments) and crystals...

Hoarded tokens and crystals serve you nothing.

But what do i know...i have only been playing for 3+ months.

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One more thing...when you buy a gear from a shipment, whenever possible, always buy the end product...not it's components...it is often cheaper that way.

For example...

This end product costs only 1k crystals.

It can be built using these two components.
60 component As = 780 crystals.


And 50 components Bs = 400 crystals.


(780 + 400) are more expensive than 1k crystal (the end product).

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Good luck and have fun playing.