Hey there,
I just pulled Costume Vanda While I imagine from what I’ve read already that the majority will say that she should be the next one to max, I like to check things at least one more time 
So, Vanda or other alternatives lile Lady Loki/ Tyr/ Russell/ Yang/ Khagan/ Baldur/ Elena/ Reuben?
My other maxed Fire 5* are Black Knight and Elizabeth.
Vanda, specially if you do not have Garnet/Grazul.
Best for ofense and decent for defense, costume version with 3 turn protection is great.
Second vote for Vanda
I have Vanda (no costume) and take her everywhere. She gets my vote.
Another vote for Vanda. Heal steal and ailment shield counter just a lot of heroes, especially at very fast speed when you can easily time it perfectly.
Thanks for the feedback everyone! Vanda it is