When you hoard crystals for a big event what is the best way, specifically, to spend them.
Spend them on energy refreshes during Galactic Chases and Double Drops events (where you want to refresh all the regular times + the next most expensive refreshes as well).
Unless it's Double Drops, it's less expensive to buy Kyros for crystals in the store than to purchase regular energy refreshes at the 100 crystal level. So **if** you're doing all the 50-energy refreshes that you can and you're still running out of kyros, spend on Kyros in any situation where waiting isn't an option.
This is the case in situations like the Grand Inquisitor event. You have to have your Inqs ready on a. very specific date or you miss it. So spending now means getting the toon 3-6 months early. In that case while you **could** just keep spending 50 crystal refreshes and eventually get the Kyros you need, the deadline forces you (or can sometimes force you) to either either spend more than just your 50-crystal refreshes or miss out.
In that case, spending for Kyros directly from the store is the best deal you've got. (Although this assumes that you've also looked at other spending options, like Grand Arena currency, and you'll still fall short)
If you're in a situation where your other sources will allow you to buy enough of some rare g12 gear OR Kyros but not both, spend the other currencies on rare g12 gear since Kyros are a (slightly) better deal when purchasing for crystals.