New player inventory question

Hey guys I'm new to the Monster Hunter series and having a good time on Wilds so far. I'm just slightly confused about the inventory system.

I see that I can only carry a limited stack size of consumables in my main inventory, but how does the field pouch work exactly?

It seems like most things that I collect in the world goes into the field pouch, but some things don't and get dropped on the ground if I can't hold them? (not really sure why this happens sometimes) Is the field pouch limited? I've been going back to my tent regularly to dump stuff off just in case.

Also what should I always carry in my main inventory besides potions?