ok. so here's a list depicting what canon characters are available and what ones are taken but if you choose garnet you automatically get ruby and sapphire.(sorry for the spoiler for those who haven't seen steven universe or are just starting.) ones without usernames beside them are available.
Garnet(ruby&sapphire): LynnMouri
Pearl:
Amethyst:
Steven:
Connie:
Greg universe:
Peridot:
Jasper:
Lapis lazuli:
Yellow diamond: