Ascendant Energy and Shards can't really be farmed. The best way i've found is to 'chase' the public events. (google the destiny events timer), that should give you an estimation of when and where the events will be. Also collecting the chests on the raid tend to build up the numbers. My fireteam each have 3 characters, varying from level 26 to level 29. We run the raid 3 times each week, trying to distribute our levels evenly, so that each run is within the same boundaries of difficulty