Problems with Item drop and inventory system

I am currently working on a game where the player kills a creature, and the creature drops chemicals that can be crafted. This is a three part question- I need an item drop system, a crafting system, and an inventory system.

First, what I have tried- For the item drop system, I tried a parenting system, so that the creature would have the mesh inside it, and when the creature got deleted from the scene, the chemicals would get dropped where the creature was. This did not work because the creature would take the chemicals with it when it got erased. My second attempt was having the creature and the chemicals parented to the same blank object, so that the creature could not delete the chemicals. This still did not work, as the object began to jitter as soon as the creature was deleted.

The crafting system was a problem, because you could not change the angle or the scale of the object, or it would not craft.

I didn't even attempt the inventory.

I want to learn, not just get code.