IIRC, I've only done 2 USB selects, and still haven't bit the bullet on the 500 gem select so far (probably waiting til the last day before I do).

Vivi - I don't use the SB as much I thought I would, but he's still going to be a main player in the IX torment once I take that on, and he did a ton of work against Manticore. Not only that, but a great +fire mag stat stick and my first SB for a character I liked still makes it worth it.

Elarra - The hype was real. Without her, I don't think I would have had the patience to grind out a lot of the magicite that I've beaten it.

I've asked about the current 500 gem USB select, and it'll basically either be Laguna, Aerith 2, or OK mUSB. Probably Aerith, as that is not available with anima lenses IIRC, and Laguna I don't think would be enough for Syldra based on what I already have and what I read here.

As far as fest goes, I think I would only do an ASB select. Leaning towards either Terra or Sephiroth. Terra is a personal favorite, and I certainly wouldn't mind a better +fire weapon for her, and it can help seal the deal for torment since I've gotten close to clearing it but the last phase kills me too quickly. However, Sephiroth really wants a +dark katana, especially since I already have his USB2... but I might just get the BSB2 from Acolyte Archives and call it a day. I forget if Rydia's available, but if it is, that would be a contender too.