Court of oryx. You don't even have to really participate, just shoot at stuff from the sidelines. But my luck has been with the strikes. But you need a fireteam and do 4 or more strikes in a row. The rewards multiply the longer you stay in the heroic strikes. By the end of 4 strikes you should have 4-7 purples and a ton of blue. When you get a blue with higher light level, infuse it to a piece of gear you like. Even if its just a few points higher Only turn in one or two engrams at a time. Check the light level and infuse or equip if needed, then continue to decode the others. Rinse and repeat. But overall the court of oryx has the fastest engram drops. Just sit there and play. Use yours or wait for others. You still get drops.