I'd say the fastest and best way is to run Crota every week (obviously) and hope you get radiant shards and armor. The problem I've ran into on my alt characters is I'm always running out of plasteel plating and hardonic essence but I've never ran out of sapphire wire. Once you get all the armor on one character transfer all your shards over to the character you're trying to get to 32. And when you get at least 1 32 the other 2 are pretty easy as long as you get the armor drops. Also try and find some people to carry your 27 through Crota at least the lamps and bridge. I hope I helped you out, I did kind of point out the obvious things but if you ever need help feel free to add me my psn is the same as my name :)