I’ve had a break, Onslaught is good, but the drops are random and no way of focusing on a particular drop(apparently there was but it was removed). The weapons are potentially very good.

It's gonna be overwhelming for quite a while then :( I've done this regularly & it's gotten really bad now with so much to unlock & no one playing the old content. Best advice I can give you is don't think too much about what to do, just try to complete something every time you log on, lessens the load over time. Have maximum glimmer boost mod on your ghost as you need glimmer to buy everything & it saves time farming it when you're in a pinch, when you're maxed go buy fragments & aspects from ikora & the stranger on Europa. Don't worry about levelling, it'll take care of itself. Get stuck with a quest or mission, YouTube it.

dont

Ooof... Well personally I would prioritize unlocking all your available subclass abilities. So if you & your bud own Lightfall I would start there & get your Strand kit. As you're doing that use any available glimmer you have to unlock fragments & aspects for your light subclasses from Ikora. Once you've got all that just dive straight into The Final Shape for your Prismatic kit. When all of that's unlocked you can double back & hit up Witch Queen to get access to weapon crafting and then just grind up your power in whatever way you see fit. If you don't own the expansions then it's just the light subclass abilities you need to buy & the power grind. Good luck :)