Best way to gear up crew?

Crash41

I have quite a few 4/5* crew members fully ranked, but stuck at level 50, 60, 70, 80. I gear them up as often as I can, but some of them need obscure mats that can only be won from shuttle missions or exploration/space battles that I still haven't unlocked.
I'm full up on space in my roster, so I can't work to collect new crew. How can I get the gear I need in order to level up my mid-range crew so I can Immortalize them and clear my crew space?

Sven Lundgren

Replicator is a good option for stuff like that.

Mururoa

Also dont think you have to keep and level all crew that pop up in your roster.
Use the Did Not Airlock list to select and focus on one part of the game. Feel free to space out useless crew.
So, as you kinda begin, focus on clearing all cadet missions. Then you can freeze all level 1,2 & 3 crew so you can free slots and use warp for daily cadet missions. After that you can go to complete easy collections and then, with the bonuses earned, you clear all episode missions.
And dont try to level all the crew around but select from 3 to 9 crew and level only them. Mark them with prefered crew. Learn to free slots by leveling easy 1* and 2* and freezing them.