capped on allagan tomestone of poetics - what can I do with them?

[Rilifane]

If you're into Relic Chasing, you'll never have enough poetics. Otherwise, what Mollusk said.

This. Relics ate my tomestsones. All of them. No mercy.
ARR is pretty tame now but HW relic still eats thousands of poetics with no way to lower the costs for the most part.
If you want to actively play some other combat classes, the (augmented) 50/60 gear is always worth investing into. Otherwise: mats.