I would choose for my teams...
Cap / Winter Soldier / Agent 13 (or Scarlet Witch if she's not made)
Iron Man / Black Panther / Black Widow
Being an old Mego collector from way back, I don't set my figure displays up that way. I don't try to recreate movie stories; I make up my own stories with my displays. Right now I have four bookshelves devoted to Hot Toys:
1. Avengers: Cap, Iron Man (mark 33), Thor, Spider-Man (ASM2), Black Widow, and Superman (Christopher Reeve head on a Cavill body and outfit.) I'll be adding Ant-Man and Civil War Scarlet Witch to that set as soon as I have them.
2. Bad Guys: Hulk (always was a bad guy when he was one of my Megos), Iron Monger, Red Skull, Winter Soldier. The bad guy shelf needs more bad guys. Ultron and Yellowjacket will be added soon I hope.
3. Batman: Returns Batman, Hit-Girl custom (she's his Robin), Ledger Joker, Scarecrow custom, hopefully I'll be able to add a Pfeiffer Catwoman some day, and maybe even a Penguin. I'd even take an Uma Thurman Poison Ivy if someone made one. But not a Jim Carrey Riddler.
4. Cap's Secret Avengers: not the Civil War team. Cap's secret team in my collection consists of Stealth Cap, War Machine, Ghost Rider, Groot and Rocket. Planning on adding Falcon, Wonder Woman, and Doctor Strange eventually. Might add a Tobey Maguire symbiote Spider-Man too.
As for the Civil War movie, it looks like I'll be picking up Scarlet Witch, Crossbones, and Falcon. I don't generally buy more than one version of a character.