We have 7 that are at 100% or 99% translated: bn-BD, ca, ga, id, is, nb, pt.
bn-BD has a strange bug, and pt is lower priority because we already have pt-BR. So I'd propose for our next batch of new locales we add ca, ga, id, is, nb.
Trac: Summary: Add ca, ga, id, nb, pt locales for Tor Browser to Add ca, ga, id, is, nb locales for Tor Browser
I built all 5 locales for linux-x86_64 and confirmed the browsers all work and the text is rendered in their respective languages.
(After merging these patches for torbutton and tor-launcher we'll need to run ./import-translations.sh again and commit the results to make sure the translation strings for those locales are properly imported.)