New tenno has questions

I have a lot and probably will have more but mainly wondering whats going on tomorrow? I only just finished the thing to get my operator customized and ig we get to redo them but idk why? And I see a lot of other stuff but I cant find anything cohesive without being more confusing...

Also if anyone has any good yareli build ideas lmk. I love yareli and yareli primes look but im just pouring everything into abilities bc I really like using them often.