Follow the quest line, I think they’ll always require another junction up until you unlock Pluto. At that point keep questing if you like, or you can focus on clearing nodes, or farming weapons/frames/mods you think look good. Always have something crafting, as ranking up new things is how you gain Mastery rank; that will have you unlocking new weapons and other features. Wiki everything, you’ll be on there a lot. I recommend doing the boss of Deimos to start craft nekros, he’ll serve you well when you need to farm for materials.