Farm Story Collectinles - How do they work?

[Joecotta]

Trying to figure out the collectibles in Farn Story. When can you collect & is it better to hold out. I assume you need all the items in a row; if you have multiples of some of them, do you lose them, as well?

And, where's the best place to obtain gems (other than purchase).

I'm on an iPad 1, if it matters.


Thanks for any assistance,

Joecotta