Where do I find new luxury resources?

I always get quite a few of the basic luxury resources, all of which are kinda boring compared to the effect of the better ones. 

Sad isn't it?
Based on map size and variables, it is improbably you will have access to a wide range of T2 luxuries in a normal game. In order to "see" relevant curiosities, you need an apropriate tier of research in "reserach and exploration" science tree. To actually explore them you will then need appropriate "level" reserached aswell.

I mean why would I use Jadonyx when I can just build an Industrial buidings.  

Exmaple:
Why spend 10 turns building industrial building for +30 industry, when you can have +60 industry with jadonyx in one turn, and consequently build the other building in 2 turns intead. = 3 turns 90 industry.
Jadonyx is one of the strongest options out there as it enables you to build up your system quickly through whichever improvements you choose.

Koxsos nailed this one.  And like him, I was also going to argue to not discount Jadonyx's usefulness so easily.  Especially as a first improvement to build on systems you've only just colonized.  Jadonyx's benefit on a high level system is debatable, but it's still useful, but at those higher levels, you should be using higher level resources anyway.  At tier one though, early game, jadonyx is one of the best resources you could hope for unless you're the vaulters with the ability to use strategic resources instead (titanium for example which gives you a boost to both production and food).  But on a newly colonized system, using the very first turn to give that system +60 to production (which is actually a huge boost on a new colony) and then putting that additional production to use building more production and food buildings (at a considerably reduced turn count), and then using the combined production from those buildings and pops generated by higher food production to build the rest of your buildings can easily give you an excellent young powerhouse colony getting that colony up and running very quickly compared to most other "more involved" methods.

So just like with Koxsos example.  Comparing the first 10 turns for +30 production, to just one turn for +60 production on a new colony, there is no comparison.  I'd choose jadonyx in that situation every time.  Except again of course, if I'm the Vaulters, in which case I would use Titanium every time instead.

As for where to find these higher level resources.  The locations in a given galaxy is randomized every game.  But you can be assured that any system you colonize early game will usually have higher level resources of some kind on them.  They may not necessarily be the ones you're hoping for, but they will have some.  But you won't be able to see them or find them until you unlock the relevant tech in the Exporation section (bottom quadrant) of the research tree.  I can't remember the specific tech names, but what you want to look for are the techs that have a cube icon orbiting the main tech circle.  If you move the mouse over the cube icon, it should tell you that, that tech will unlock levels 1, 2, 3, or 4 curiosity detection and levels 1, 2, 3, or 4 curiosity expedition.  Specifically detection allows you to see that an undiscovered curiosity is there, but won't allow you to unlock it yet.  And Expedition level gives you the ability to unlock curiosities.  But they will be in a format that tells you that a specific tech will unlock curiosity detection level 3 and expedition level 2.  So you will always be able to see curiosities one level higher than you can actually unlock.  But it's those cube iconed techs that allow you to upgrade your ability to see and explore higher level resources and curiosities.

On a final note, as mentioned earlier the distribution of luxury and strategic resources in a galaxy is always random from one game to another.  However, I should point out in my experience that they also do seem to be regionized.  So you may find in a region that you have tons of sources of deciduous trees and zero sources of Jadonyx.  But in another region, you may find that it has tons of sources of Jadonyx and very few source if any at all of Deciduous trees.  So they do seem to group together.  I believe this is to incentivise trade between competing factions and to promote people to sell surplus resources on the market for Dust and to buy resources you need but are lacking on the market.  Also, when it comes to strategic resources.  I have found that they are pretty evenly destributed around a galaxy, except when it comes to the center of a galaxy.  I have found in pretty much every game, the center of the galaxy (the major clash point between all factions) tends to have unusually high concentrations of all strategic resources.  Especially high level strategic resources.  So if you need Quadrinix and Orichalcum and are willing to fight for them, I would generally look to the center of the galaxy for the highest payoff.  But expect to fight for them, because everyone wants to be the king of that hill.