I also got 17 coins to purchase the sniper rifle from Xur but I'm still in two minds because it's taken me this long to accumulate this many coins & what if he has the chest plate or an assault rifle next week. So I'm going to save them for now.
To upgrade later stages of legendary purple armour you need materials (which are easy to get from farming) and Ascendant Shards which are much more difficult to get. The daily mission on the highest difficulty will gift you two shards & public events or random drops is your other chance if luck is on your side.
I'm level 26 at the moment so could tag along on the raid mission but I'll just keep on dying & don't really have powerful weapons yet so will wait till I've gone up another couple of levels & got at least one exotic weapon.
With all the disappointment of DriveClub & the near purchase of a XB1 with Forza Horizon 2 it was good to ignore this & get back to gaming.
I also decided to complete The Black Garden (last story mission) to finish the main campaign. It's crap, what little story there is in the game is just a confusing pile of mess. Coming from Halo, I don't understand how Bungie could have messed up the story so much, there are various reddits which show the game had a troubled final 12 months & changes were made that ended up with what we have now.
If it was not for the gameplay which is amazing I doubt anyone would still be playing this, Borderlands Pre Sequel arrives next Friday so I expect to be spending more time playing that than Destiny. Although I will still try to play every day to complete the daily mission to collect some shards.