By RAW goodberry cannot heal. RAI and officials answers are more important than RAW

[BoringInfoGuy]

The only way to get 80 healing out of goodberry at level 1 is life cleric, human variant with magic initiate. You cast it before the long rest and after the short rest to have 20 berries for a day. You cannot use your spell slots to cast it and you cannot upcast it unless you multiclass to druid/ranger amd prepare it. Other wise, you have to wait at level 2 for a multiclassing and you will have 3 slots to cast it.

Opps, I had completely forgotten that Magic Initiate only let you cast the first level spell gained by the feat once per long rest at the lowest level possible. Apply my math to a Life Cleric 17 Druid 1 and I think it still works.

(Should have taken my advice from my first post and read the ability before posting)

On the other hand, I also missed that casting the 1st level spell with Magic Initiate does not take a spell slot.