Five Star

Good options. Honestly though, xander or Camus are best bets for all around usefulness, but alfonse and Anna are super useful for PvP and random quests.

The armor and dragons are great options as well, but your best bet is looking yo complete an emblem team, armor and horse have seen great free units.

What IVs is your CorrinM, ATiki, and Seliph? Also, what other 5*s do you have?

Nowi and A!Tiki are the best units, Alfonse and Anna are really useful as bonus units and for quests

Xander>Nowi>Adult Tiki>Effie>Anna>whoever else you like. That's just my preference based on the units I use and know are good. Though if you have Sigurd and don't want the built in distant counter you cans skip Xander.

Seems hard for you to make a sentence.
I would say depending on your needs Leon is nice, Zephiel if you plan on investing a lot, Atiki...