cave is pretty fine at the beginning to get all slots in blue and some in purple, but as you get more purple gear the chance of getting the rest in purple that you need becomes low as ... I got from the cave a lot blue stuff and some purple weapons purple shoes and gloves i got as reward from doing pvp but no helmet and no torso, so the best way for getting this was doing pvp and more pvp. in 2 weeks i earned 200 pvp points and enough reputation. think about it. in 12 minutes (max) you can get legendarys, exotics, engrams, strange coins, 2/3 pvp points, reputation, experience points, notes of light, shaders and crapstuff. and you'll FOR SURE get that stuff that is missing in your collections. there is no random in spending pvp points and buying the stuff you need. From finding strange coins i got my exotic gloves and as reward for a lvl 24 strike i got the last word handcannon. so to me the cave is only a good start and part of the mixture