With a baby gacha, it is best to use meat in the beginning. Berries are Not the right food, as it allows for their food health to go down too quickly which in turn allows for them to starve to death. Meat is best and then as they gain weight, both stone and meat can be used.
Rare mushrooms add 50 food per. Don't decay. Easy to get from megachelons. Rare flower work as well. Beware they starve extremely fast. So only food with high enough food value will keep them alive. Aka not the seeds u get from megachelons. That will cause them to starve faster than they can eat.