For competitive gameplay i think one of the best, and cheapest in a sense, team out there would be:
It requires every troop fully traited to benefit the most of all sinergies and resources gained (Souls from Valkyrie). I know it’s not a team so easy to assemble and upgrade, but compared to every other cheaper option this is by far the most versatile and competitive. Even in battles where Mab can’t do anything you can just push for the victory using the other three, in every other scenario her normal damage is not a waste even if paired with Khorvash’s true damage, because it reduces armor which will probably soften the enemies enough for skull kills.
You should keep this composition saved/noted for when you get these troops while also waiting for a chance to buy the glory packs with the traitstones you’ll need.
This thread might help with fun thematic teams, but some compositions might not be so good anymore: GoW Team Build Compendium
I’ll try to add more suggestions later.