Make an idealised version of you as MC, and obsess over it.
Make them the absolute-looker or what you wish you looked like. They're the most powerful (you don't have to provide why and how, just throw in some bullshit excuse), and is better than everyone else around them in many aspects. Sprinkle in some weaknesses so nobody can accuse you of making a Mary-Sue, but of course it should never be actually get in a way of your character's conquests, or if it does they instantly overcame it. They share your belief and constantly preach it, or make the narrative helps them to indirectly convey it. Everyone who disagree or criticizes will be antagonized. Of course, they will suffer no repercussions for misdeeds they make, either nobody brings it up on the story or everyone will take their side.
Now let's make great side characters!
- First is stand in for your friends or people you think tolerable/or tolerate you enough, the sidekicks. As you are the main character, they'll throw themselves at you to make you succeed. Their interest and purpose is to help you, fawn upon you, and maybe narrate your fight scenes. That's why you can give them the blandest and most clichéd personality as possible
- Second is stand in for those you hate, the villains. From your school bullies, people who disagree with you on Twitter, the girl who rejects you, the teacher who won't give you extended deadline, to someone you're jealous of! Make their fictional version as despicable as possible without any drop of humanity, depicting how you feel towards them in real life. They should have no redeeming quality because their purpose is just to be MC's punching bag, or to showcase what happened to whoever wrongs
you MC. They should get the worse retribution possible; death, torture, and slavery are a go-to.
If your audience are mainly males and the characters are female, it's better that they will get raped (maybe also go the Redo the Healer's path) or traffic them. With male characters, just torture or kill them off screen, nobody gets off to that. Actually, just do that regardless of your and the audience's gender. I meant females should be purer than males, right? The fact that they can become so villainous means that they're extremely messed up.
- Third is the MC's lover. Regardless of gender, they must have a flawless appearance and unwavering devotion towards MC. Gender specific types:
If male: rich, powerful, domineering, possessive, prone to jealousy, gives MC expensive gifts, sexually pushy, brood a lot.
If female: saved by MC, obedient, emotionally needy, catty towards other girls, eager for sex/having babies, actually powerful but less than MC.
If NB: make them more female/male-leaning then see above. Also they must be alien/robot/non-humans.
- Fourth is minority and/or marginalized character. Don't worry, you don't need to actually research or consult actual member from the group (I know you don't wanna talk to them). Just show MC being a good friend, ally, or even saviour for them because your MC is so kind and open-minded. That's what their purposes are.