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Uncertain About Relic Gift Advancement
(2e.aonprd.com)
So I think I found the answer to your question: the table is second gift at 5th level and 3rd gift at 10th level.
Generally speaking, this results in a relic gaining one gift for every 4 levels its bearer has, but this might fluctuate as the campaign progresses.
The above is what I'm basing it on. Hope that helps.
Thank you! I think I've gone completely text blind skimming through eveeything.