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.
Railjack is necessary for a quest later. Railjack Intrinsics is the "item" that gets exp when you do railjack missions.
Archwing is a one and done thing. You need at least one actual archwing to do things with archwing, as well as a archwing weapon and arch gun. You need this to leave the railjack to get to some mission progression points
Void keys don't do jack shit anymore. Dragon keys are still used for various tasks, one of which is a meta for shieldgating, as well as opening dragon vaults on Deimos (not Orokin Derelict anymore), for corrupted mods, which are still used.
Fishing and mining are necessary to build certain items or parts for weapons/Warframes/etc among the open worlds.
Building your own companions is only necessary if you want the mastery exp, a loot multiplier, and mining/fishing helper, or an undying battle pet.
You need your tenno to do various things and earn arcanes. I cannot stress enough how important they are by late-game.
Conclave is fucking worthless. Only do it if you want the cosmetics.
Rivens are fun, but not necessary, once you have nothing else to do, you'll end up collecting a lot of these.
Once you're done with the star chart you can do star chart 2, aka steel path. All enemies are level 100+.