A few questions

I'm currently level 52 and I've used Bahamut and Tiamat to get my primary dragons up to level 20, I'm currently struggling to save food for the elder conversion. Is there any best food to farm at this level? I am currently going with jelly plants

​

Additionally I've been trying to get the Tien dragon through the cooperative breeding cave, I've had no luck for a month :(

I really want to save up some DC to get a bunch of islands so should I start a small DC farm now? At least until I get the Tien one going. If so, which dragon do I use? I have a Corrupticorn and a Yarr from the event

​

Do I spend my etherium on clearing the rift or do I just use it for habitats(and maybe the occasional egg of mystery) since we can clear one a day for free with ads?

​

I currently have all the habitats you can only get with gems other than the Chrysalis habitat. Both my breeding caves are upgraded so what should I save my gems up for now?