For anyone wondering what to spend their renown on: I'd suggest going with assortment of jewels, or the Mountain-sherd. While all the options are 1:1 per penny, these two in particular don't have other great sources. (Though, keep in mind there aren't all that many uses for these items currently.)

-Sapphires and Venom-rubies don't have any end-game competitive sources. Mostly the Sapphires. Rubies can be grinded through Curator's Gratitude, which is decent. The diamonds are easy enough to get though various sources, such as Khanate crates.

-Mountain-sherds are currently only available through Underclay or Unprovenanced Artefact gacha. If you wanted to grind out these in bulk, you're looking at ~3 EPA at best. Not great.