((
Good day !

There is no sole 'best' path for gear - some may want to ignore lower armor, but if you plan to spend a long time in the lower 70th season, or learn all available and interesting AA at each season before moving on to the next one, as I did, then it is better to have the best available gear - cultural, symbols and seals - for your season (it makes hunting simpler), rather than use weaker armors and wait for a higher one to be unlocked.

Phosphenes are either earned in Solteris raids I think, or the simplest way is to use the Loyalty system, from what you earn weekly and the Loyalty merchant in New Tanaan, to buy a bag of them and then right click from a top slot to retrieve some.

I have heard the same figure of 2350 but I never checked myself.

I do not know who can buy the gear - I never bothered with Solteris Gear myself - but I am sure you can find someone in the General channel who is Solteris flagged if asking politely. Some might offer to do so for free, some will expect a fee to take the time to do so...
))