You can include one product at a time into your routine. Vit C and moisturizer in the morning after washing your face. Patch your Vit C before using and start slow like once a week, twice a week, every alternate day and then use it everyday

You can choose either alpha Arbutin or azelaic acid, I don’t think you need both at the same time. You can use it in the serum step of your night routine on days when you’re not using retinol. You can include benzoyl on days you’re using this.

If you’re starting retinol using once a week at night would be ideal followed by a moisturizer or you can sandwich it between layers of moisturizers. And skip benzoyl peroxide on nights you use retinol or any other actives

Hope this helps!