Motes of light are not that hard to come by if you do your Daily multiplayer(usually 3000xp) Daily mission(1500xp/4500xp/7500xp) Weekly strike(Xp bonus) Nightfall(grants %25 bonus xp untill weekly refresh) And many bounties ranging from 2500-5000xp So RNG makes sense cause you can get so much of it Stange coins are different where itll actually garentee you getting stuff from Xur that's why you're limited to a max of 9 per week for each character Most of the coins I get are from Decoherent engrams RNG does suck but that's what makes the game good cause you don't know what you might get

Spend 23 motes of light to get a warlock helm (I am warlock so bonus) and ended up with LIGHT BEYOND NEMESIS so that got stuck in the vault as it's the ugliest helm I've seen like a biker crashed into a flock of crows and got him helmet stuck up its a**e