Play whatever class you find the most fun, in open world I see mostly scourges, dragonhunters and berserkers. I think any event in Dragonfall or Bjora Marches, you can get eternal ice and mistborn motes to trade for ascended accesories (in Bjora marches you need to do two collections to buy them), farm winterberries for other ascended accesories. I can play fractals for a chance to get gear chest (t3 and t4), craft them yourself or buy them in fractal lobby for some gold and marks which are craftable