i'd recommend watching some videos off of the nct daily channel(it's inactive now) like awsaz (awkward but it's ok), welcome to sun&moon, and videos from resonance era (nct2020). also the 24hr relay cams for all of the members.
>for nct 127:
you can watch johnny's communicate center, nct 127 hit the states, the stick together series, fill it up series, and the late night punch show
chenji's this and that, dream vs dream, 7llin' in the dream, 7llin' in our youth, and mental camp.
the dream launch series ( i think it's called dream plan), way-variety videos, and winformation.
>on the main nct channel:
master moon chef, the nct show in the nct universe, what's up sungsho, the newer jcc, chenji and awsaz videos.
but really, take your time and start wherever you like. i'm sure other nonas will chime in