Breaking this down...
Sequence A - opening of Gillis being dead... the scene of him in the morgue (touching when a little boy wakes up in there) that was cut in the final film... Tells the story of him being chased for money, winding up at Norma Desmond's place and moving in. Have set up Sheldrake and Betty.
Sequence B - Gillis wants to leave but can't because of money and accepts clothes from Norma.
Sequence C - Gillis a kept man... he tries to leave but Norma tries to kill herself and she and Gillis sleep together.
Sequence D - a kept man, gets call from De Mille, finds out its fake ends on her going mad
Sequence E - Gillis sneaking out to write script, gets busted... dumps Betty and tries to leave but is shot by Norma.
It's a Faustian tale I suppose - or like a vampire movie, with Norma as the vampire sucking in Gillis. There's a lot of compassion for her though - and Gillis is a bit of a shit. Betty is the one nice character.