How to get soulstones?
I'm not sure what the actual question here is but the answer is the same. If you are asking about soulstones, they are usually obtained through official events (i.e. purchasing them at the bazaar, etc.). If you are asking about fortuna tokens, you get one free token a day when the fountain is open. To get more tokens, again you obtain them through official events.
Personally, I'd like to see both available through purchasing them at the warehouse by trading merits.
As explained above, you need the Fountain Tokens to get that single soul stone.
However, Fountain Tokens are stupidly rare, even for paying players. I can't remember the last time I've seen a token for sale in the Bazaar.
Regarding Merits, another tier or even new Artifacts would be a great. Or cost us merits to buy more slots for the pre-existing artifacts. Anything would be good.
Traits were probably meant to be a Merit dump for a lot of people, but the results that I've seen have been catastrophic. 100k merits for only two 5/5 traits is a pretty stingy return.