Hello!
Im fairly new to Sylvestia
(i believe my account is 3 or 4 days old when im writing this)
and i still have not figured out how, when, and where to get essences.
If there is a certain area on the map that you usually find essences in
(would be helpfull to know) anyway that's just how i think you get them
So it would be a big help for you to fill me in!
Thanks a whole bunch!!

You can buy essences in the diamond shop, and you occasionally get them when nurturing eggs. I'm not sure if there is any other way to get them.

You can get essences from nurturing, battling, or mission satchels. All of these are rare drops.
There's also a chance to get essence from Jinxie Jamboree. I personally don't play that, so I don't know the drop rate, but it should be pretty rare as well.

You can buy from the diamond shop (using diamonds), or from other players on the trade broker (may be expensive).

Well if you're buying from the broker the Essenses have hit an low value spot for the time I've been here.