If you lose the battle, the village keeps all loot, and you gain nothing but wounded units.
Do not land ranged units (Archers/Sulphur Carabineers) in the first round; they are ammunition-dependent and should be timed to arrive as the wall falls to save shots .
Example loot for level 5 village: ~2000–3000 total resources.
Pro tip: If you see 50+ steam giants, skip that village or return with 3x that number in ranged units.