tho this refers to the first episode of a storyline, this is still valid

im gonna edit this for literature: your "first ep" should be your first 5-ish chapters

while your first chapter should be interesting, it shouldnt try to be a first episode.

your first five chapters should introduce a setting, your characters, a basic set up (maybe even allude to a storyline), and include a "oh heck" moment

he explains the "oh heck" moment really good, but lemme break it down for books-

nfh 1-5: victor and umbra are introduced and we learn their set up. magic is revealed to be common place (oh heck), they receive a mission and are the chapter cuts off with them teleporting

world eater 1-5: alzar and sariel introduced, with their set up and basic character traits brought up. abaddon is revealed (oh heck), the storyline of alzar going to counseling introduced

hth 1-5: grim and moony's characters and dynamics are introduced, along with hades. grim's slacker personality is stated, alluding to the rest of the story. i would consider the "oh heck" moment when they reap the woman in the car crash

as a standard, if nothing interesting or cool has happened before chapter 5 you're probably doing wrong

do give the video a watch. he mentions about writing in the serial format (what's the difference between episodes released weekly and chapters released weekly?) and how to take care of binging versus following a series.