First, to unlock them you have to complete achievements that are very likely hard to get without those resources.
Then, when you have them unlocked, you have to get a very specific set of ambassadors to create them, but i'm seriously wondering about some of them.
For example, Oil (with can probably be very powerful, and i'm not even sure I've unlocked it already or not). You can only get it from silver (the wiki states that you can get it from platinum... but you can't place platinum on a swamp, so basically it's a joke). You have to get a very specific set up of ambassadors. So, you need to upgrade your silver with a sublime seismic aspect, so 2 swamp ambassadors for a giant. And obviously at least one desert and one other : a desert one would give greater noble aspect and level 3 minerals, but if you take a forest one you have to get a cristal aspect to upgrade a salt mine into an onyx to upgrade it to silver.
But anyways, you're stuck with your sublime seismic aspect.
So, my problem is : It takes a LOT of planning just to get ONE resource, but most of the time I'm getting crappy projects due to the randomness. Something like "more tech from opium poppy !" that requires 3 swamp ambassadors. Well, I've not planned on creating opium poppy ? I'm screwed.
It's up to the point that I'm not even bothering with level 3 resources, just focusing on getting the stuff I need and just getting every superior resource, the rest being just random as i go along.
So, how do you plan with level 3 resources ? Have you a specific plan or do you just go along ?
Edit : damn, wrong forum.
Well, it's in "Ideas" so...
Is it possible to have a "ressource tree" accessible somewhere in game to facilitate planing ?
An option that shows you what can upgrade to what with nice arrows and stuff, something like
Chicken ----> Rabbit ----> Deer ----> Moose
-----> Beaver ----> Boar
Edit bis : made an image, something simple :

That's the idea