PoSky - advice needed

Hi All, I did my first visit to Plane of Sky and thanks to some really good video guides, managed to get all keys, clear the bosses etc. on D0.

My question is, when people talk about farming Sky, what does that mean? Now that I have all the keys, should I just kill the island bosses, or also all of the trash mobs? Is there any benefit to doing it on D1 and higher, except that you can then probably do several runs each day? What would be the best course of action, now that I have access to all islands? My trio is war/brd/dru in case that matters.