Pick out your pants first. It sets the tone for the rest of your outfit.
Once your pants are fixed, the rest is surprisingly easy.
Shoes should go next since they fix the formality or whimsicality of your outfit.
You can pick underwear depending on how likely you are to be seen in them for the rest of the day (the less you’ll be seen naked, the uglier they can be).
Then move on to your shirt. It should complement your pants.
Jacket and accessories go last.
Note that this is the order for planning an outfit, not putting it on.
- Shirt (so it can be tucked in if desired)