You can get the "Big 4" as arena milestone rewards. My suggestion would be to spend 25 gems on the weekly dragonforged chest. I have an android account I mess with when I'm bored, and I got a Gunslinger's Trappings + from a chest, with starting combined stats over 2K. The B4 are no longer as useful as they once were, even for beginners, since they changed the monsters in the story map stages. Whereas, for example, the Relic Ruins only had earth element monsters, on the epic stage the main boss is Medusa, which previously you didn't encounter until Skeleton's Tomb. The main boss on Skeleton's Tomb epic stage is now a spirit/air monster (can't remember it's name). The Bigger 4 aren't much help either, so I would either go with opening chests in the hopes of getting something good, or follow hoticehunter's advice.