How do you start to organize a closet from shelves to hanging poles?

It's all a puzzle of common sense. You know what clothes, shoes, hats, bags, scarves, coats and gloves you have. Build what accommodates what you currently own with room for expansion. I group like items together, then by color. I separate the dark colors like blacks, Brown's and navy by placing white, cream and other colors in between so you don't mix them up (I get up at 4 a.m., it's dark!) I would do a dual rod, upper and lower. Blouses, shirts, etc. on top and slacks on the bottom. Then count your shoes and boots, again with room for expansion. Build what will hold them. Visit a closet showroom or even a big box home improvement store for ideas that you can build yourself.

I hang my clothes by weight, then by color. For example tops are sweat shirts, sweaters, long sleeves knit, long sleeve lightweight, short sleeve knit, short sleeve lightweight, tank tops. I like dark to light left to right. Consider using flocked hangers like huggable hangers. They are non slip and don't take up a lot of room.

Maybe this will help :)

https://www.realsimple.com/home-organizing/organizing/closets/12-secrets-closet-pros

I tend to colour coordinated. I put all my skirts and tops this way. I have lots of clothes.

Or you could put outfits together for quick picks.

Shoes are great on open shoe racks or in clear boxes, but it depends whether you are a tidy person. If you aren't then you will probably find a rack shelf would be better, so that you can reach in and grab rather than sorting through boxes.

Drawer unit with sections init would be great for underwear and socks. Scarfs and belt hangers are useful too.