If his mind was purely on hatred for women, he would not have had the thought of killing those 3 guys first
His mind was never purely on hated for women, but his rage toward women, and the men who got the women, was definitely at the core of his paranoid delusions. He was obsessively preoccupied with that, for a very long time, and everything else followed from that. And he continues to state his hatred for women, in no uncertain terms, until the very end of his manifesto. The media was not biased in reporting that. His misogynist rant about women was like a crescendo at the end of his manifesto.
The more he engaged in violent gory revenge fantasies, the more out of control he actually got regarding his targets. At the end he wanted to just lure people to his apartment and torture and kill them--that's allegedly why he killed the roommates first, to simply get them out of the way. In his mind they were just collateral damage. Then he'd go on to killing other people in other locations. He just wanted to kill. And what he did to his roommates, just shows the horrible, horrible depth of his rage at that point. And the rage wasn't even toward the roommates. He just wanted to kill and mutilate.
His actual shooting spree wasn't really well planned or carried out at all. Considering the magnitude of the violence he wanted to do, he really fell short. He had checked out and selected that particular sorority house. He had planned on entering the sorority house to shoot, and after killing the women inside, he wanted to burn the house down, but he never got out of his car, he just shot at the two women outside of the house.
You're not going to be able to figure out his logic--he wasn't being logical, he wasn't thinking rationally, he was delusional. The fact he killed his male roommates first doesn't tell you anything about the source of his rage--his rage was mainly toward women, he makes that very clear at the end of his manifesto, but the violence he wanted to express, stemming from that rage, was directed toward everyone--toward humanity. This was his ultimate power trip.
Humanity has never accepted me among them, and now I know why. I am more than human. I am superior to them all. I am Elliot Rodger… Magnificent, glorious, supreme, eminent… Divine! I am the closest thing there is to a living god. Humanity is a disgusting, depraved, and evil species. It is my purpose to punish them all. I will purify the world of everything that is wrong with it. On the Day of Retribution, I will truly be a powerful god, punishing everyone I deem to be impure and depraved.