Best team I can make?

id have to guess Keqing with Baizhu, Fischl and Sucrose
Keqing can use Furina sig. isnt much but its still somewhat better than Lions roar

you have a ton of good options between freeze, overload, baizhu hyperbloom, reverse melt, keqing aggravate, taser, teams where ayato is the driver, etcetera

Ayato is a good dps, together with Baidou and Fishle it's already a good team. But you might want a Sustainer for the team. I would prefer an electro or Hydro healer. But your arsenal is a bit limited. Baizuh is a Great healer, I think I would go for him. He messes the reaction a bit up, but that's fine. Bloom isn't bad but you sadly don't get hyperbloom triggerd as good as other chars