Pairing Ophelia

Boey, Lilina, S.Sharena, and Soren can all be good pairings for Ophelia, S.Sharena can lower Atk/Res on the slowest unit, Soren can lower the highest Atk, and most people run chill Spd/Res on him also for the double chills and for this team up Chill Res would be better, Boey can protect her from axe/lance/bow units maybe Blue mages and low atk green mages (pretty low res), Lilina is a pure nuke along with Ophelia

I think she'd pair well with green or red who can do some degree of tanking. I'd say my top 3 would be:
Lilina: can reach respectable resistance and will nuke any greens that threaten Ophelia.
Spring Sharena: fast with good resistance and does debuffing very well.
Aversa: Good fun with her tome debuffing and panicing while she has decent all round stats and could provide Guidance support.

wait which special are you talking of?
caus with her default she needs 2 mages to have it instant trigger..

non the less i really like bridal sanaki as a mage, but she only really shines in a flier team (with her prf weapon or bladetome)

Morgan: meh

Delthea: more blue? not really

Tailtiu: see loli vampire

Micaiah: see loli vampire

Spring Sharena: good option, depends on ivs

Nino: if you´re not as bored of her as me then a good viable option with high merging potential and easy to find good ivs

Odin: unless you want to do father/daughter -> see loli vampire

Robin (m), Reinhardt: see loli vampire
// why so much blue :'D

Boey: good option with merging potential but needs CC to really shine imo

Soren: see Nino, but has prf weapon

Lilina: really like her, but has a similar playstyle to Ophelia (Special Spiral Oneshot), so could be al little boring having two almost the same characters on a team... but has good merging potential so yeah idk, comes to your preference..

Aversa: really good mage flier, when you´re not planning on merging much in the near future i would give her a go since shes useful in almost everything (Arena/PvE) thanks to her prf weapon

Robin (f): well green, higher def... boey would be better imo

If you want a good base team i would go with
Ophelia, Aversa (Lilina -> too similar to Ophelia)and either Nino or Boey (Soren is good at debuffs but you have Aversa, even though she can´t do everything)

So yeah hope i could help. Keep in mind that is my opinion, you don´t have to do it^^

//sorry for the long post btw :D