Are the Kirin's tops actually worth buying?

[Jzarah]

I've started doing Eureka as I want the glowing Anemos rapier and the ability to dye my level 70 Dragoon gear. I've seen recommendations to buy the Kirin's Osode of ___, but depending on the gear class they cost upwards of a million gil. Should I actually buy one, or does it not affect much if I don't intend on going past Anemos?

[Shadotterdan]

You can get through Anemos without it, though with it you could likely solo your way through it instead of finding groups.

[ItMe]

I've beaten Eureka and until your post I had no idea that gear even gave Eureka specific bonuses.
It's not needed.

[Curisu]

You should not buy the piece itself but the 2 materials that can craft it.
The seals should be a lot cheaper itself.
The NPC to exchange the seals into armor is on the wood part of the pier where you enter eureka. I don't know the English Npc name.

Does it help?
Yes, a lot. It has spacial stats that increase your survivability.
Do you need it? No, with the echo buff you are already a lot stronger then when it was "new" content.

But why stop at anemos? So much more content is there and the Bunny fates on the last 2 islands are a great money maker.
Also the Ozma mount after you finished BA.

Every DC has dedicated Discords for Eureka and BA, and these people are happy to help some new player get through the content they like.