First things first. Head to the Eternity section on the destinations tab and go to The Rite of the Nine hub. There you should be able to claim some weapons and armour that will jump start your journey. After that I would just make your way through all of the campaigns that you’ve missed. I’m unsure what’s included with that pack but it shouldn’t be hard to figure out what order to go in. That should keep you busy for awhile at least.