uhhh no idea, but I only use 1 mincost bronze soldier (leo) myself.

you can use 2 soldiers (katie + julian), let phyllis rot. both 50cc'd.

you can forget about awakening units for now since you're most likely still quite new. but if you do, requirements are:
The unit needs to be of Gold or higher rarity
The unit must be CCed and at max level
The unit needs to have 100% Affection/Trust
All units need a Spirit of Awakening, Purchased from the Trading Post for 100 Demon Crystals
Either 200k, 250k or 300k G, depending on if their rarity is Gold, Platinum or Black
3 class-specific Gold Units or CCed Silver Units
you still need to level the plat mage anyway since you need a good plat+ mage for magic aoe dmg.