How does Faster Casting work with Totems?

What happens if I use a totem with Faster Casting? Will casting totems be faster or will the totem cast faster? Or both?
What about Item Rarity?
I've just gained a totem gem, but I don't have socks for it, when I use it will it continuously drain my mana?

The totem will cast faster. And if you link item rarity/quantity to it it will add that to the totems kills.

Thanks for the answer. I was also interested in knowing.

Both the totem and the linked spell will cast faster. It's a very good support for totems.