Hand bag is the last item chosen; that's because I keep all my hand bags near the front door. Usually I have a pretty good idea which one I'm going to choose, but I have been known to scuttle back and forth between front door and bedroom full length mirror to double check if the handbag works with the outfit, before I swap out all the contents.
The down side to this strategy is that I can forget I own certain purses. For example, I have a cobalt bag that has not seen enough use and that's a hot color now. So I will probably try to plan around that bag for awhile.
Otherwise, I plan according to what the day has in store for me. I don't work every day in an office. Every day is different.
Do I need to go errand running? Flat comfy shoes, and probably a layer because I freeze in the grocery store.
Do errands include hitting up the mall, where I might try on clothes? If I'm going to shop for dresses, make sure I am wearing a dress with proper dress underwear. If I'm going to shop for pants or tops, don't wear a dress. And wear comfortable heels so I can check pants length. No buttons on top because getting in/out is too difficult. No boots for same reason. Is there an item I'm shopping for a coordinating piece? Wear it. Yes I think all that through.
Am I meeting girlfriends for lunch? They'll likely be dressed from the office, so might as well dress as if I have also been at my office.
Am I going out and about with my teens with or without their friends, or will the friends be hanging out here? Take extra special care to dress my age and look "grown up." Since I'm shorter than all of them. But don't go overboard and look frumpy and dated; remember I am their role model for what it means to dress "grown up."
Am I meeting up with accountant, lawyer, doctor or some other professional? I like to dress respectfully for such occasions.
Am I canvassing for my favorite political candidate? Wear blue, and comfortable shoes.
Am I going to be walking on cobblestones? Wear flat shoes or wedges.
Is today an in-office day? That means I'll be on video conference. No patterns. Pearls are a must; no silver/gold. Something with a strong shoulder line in a flattering color.
Am I going out after work hours? If so what are we doing? Dress appropriately for the occasion. If coming from the office, how can I swap accessories to go from day to night? Are we going to the theater? An art reception (dress creative/trendy)? A movie (dress warm)? Dancing (wear heels)? What neighborhood will we be in (each has it's own style)? Etc, etc...
Am I seeing my Mother-in-law? Dress in something she hasn't seen me in yet. She loves to ooh and ahh over my outfits, and she's a fashionista herself.
Possibly I have over-thought your question, but it was fun answering.