I played last 7 or 8 years ago, so many things changed.
How is creation of manastones now?
Which items T6 or T7 do we use and where to farm the items? Is Talaghan region the way to go, or only in dungeons ?
And i remeber there was a cheap fusion stone like 3k gold, now i can only find 11k or 12 the cheapest, ist this intended for gold sink?
Thanks in advance 
Most people farm in Ice Blade Plateau, there are clean items dropping you can use for crappy or clean stones. The Arcane Transmutor was changed on CoA, so it includes all purified fusion stones and randomized crappy ones in it by default. By right-clicking purified stones you can add them into the transmutor easily. There are plenty of addons available that replace the old "fusion", but no idea about that, since i don't farm them myself... maybe have a look on curse 👀
I noticed too that fusion stones for gold are more expensive here. I'm not sure about the under 3k stone, but the around 5,7k i used to buy with 1 sta and 0-2 random stats are aprox 11,2k here. The NPC that sells them is the same, except it's in lost island of atlantis now.
Arcane transmutor has a build in random fusion stone feature, the second option out of the 3 available (first is regular arcane transmutor, 3rd is the ones which stores and uses purified fusion stones), and this random fusion stone option uses up 10k gold instead of a fusion stone. So you just click on the 2nd option, place the item you want to use, and it will cost you 10k gold instead of placing a fusion stone.
About how high the tier for trash items - i dont know, i'm not an end game player yet, but i asked in my guild and nobody knew if there was a place to farm trash T7 or T8 items for tiering. It was one of those awkward silence moments, followed by "we dont know" . As far as i've seen on AH T7 or T8 are dungeon (or possibly crafted) items. Phirius shells gear is T6.
