I would suggest “any good BLUE MANA troop” in first slot. Hero works up in front as well when using a blue or green weapon. Treant (blue/green) shows up very soon from Glory chests.
Valkyrie is there for the soul generation whenever you use her ability, and Alchemist will generate gold revenue.
I guess you guys aren’t aware that it’s surprisingly difficult to get Banshee and even Valkyrie really early on in the game? I’ve observed this now on three different accounts (console and tablet). A player may be level 20+ before Valk is drawn, and well past level 30 before Banshee ever shows up.
So, very early game, I would actually suggest Hero(red axe)-Atlanta-Goblin-Luther. This team has three damage dealers. Be sure to complete the Broken Spire questline to get Luther ASAP because the Sheggra end boss becomes blinking &%$^! difficult after a certain point. Then do the Divinion Fields questline to get Atlanta.
Later once you manage to get the cards, you can try Hero(purple weapon)-Luther-Valkyrie-AnotherBlueTroop. In this build, you’ll only have two damage dealers, so you’ll have to play a bit more mindfully than with the goblin team. The advantage is that matches will be over more quickly because you are generating the blue mana colour you need. The previous goblin team is inherently slower despite the extra turn.
Also experiment with the Team Bonuses for using multiple troops from the same race or the same city. For example if you use Wildfolk troops, consider using Herdmaster as a mana generator in conjunction with other Wildfolk from Divinion Fields to get the city team bonus.
Hope that helps somewhat!