These are starting points. Scouting, selected hero skills and your own battle reports should refine a generic ratio.
Safe starting point against an unknown opponent.
Replace it with a scout-based counter whenever possible.More frontline durability for structure or city defense.
Use defensive leaders and joiners.Durable garrison with all three troop classes active.
Adjust against the scout and the selected leader skills.Archers pressure Infantry while a viable frontline remains.
Dangerous when the opponent has meaningful Cavalry.Cavalry pressure the enemy backline.
Keep enough Infantry to hold the frontline.Infantry absorbs and counters Cavalry.
Do not leave Archers exposed.Damage-focused starting point.
Compare with your own battle reports.Extreme damage test.
Never assume this is universally optimal.