Is there a new player guide on what to do / focus on?

While not technically a new player, I might as well be. I played back when Loki was my starter frame, and I don't remember the planets being locked on the star chart. I have started over on a fresh account to try to learn the game, but holy cow there's so much going on I am completely overwhelmed.

Do I need to really learn the following systems? Can I ignore any of these until later on, or do I need to focus on some now?

Railjack

Archwing

Void Keys

Fishing

Mining

Building my own weapons/pets/robot companions

Levelling up my Tenno powers

Conclave PVP

Riven mods

Trying to figure all this out while getting mastery ranks to unlock more trades and new weapons is a lot of mental overhead. Also, will there be stuff in the lategame that is more challenging and requires me to actually upgrade stuff? It's pretty easy so far.