A capsule wardrobe is an editing exercise, not a challenge to own a particular number of clothes. The useful question is whether the pieces you keep help you get dressed for the week you really have.
Map a real week
Write down what you wore for work, errands, evenings and weekends. After two weeks, you may find that your closet is full of occasion shirts while you keep repeating the same two everyday tops. That observation is more useful than a generic list of essentials.
Build outfits on the bed
Choose one pair of trousers you wear often and put three complete outfits around it. Then repeat with another bottom. Lay everything out, including the layer and shoes you would actually use. If an item only works with something you do not own, set it aside and decide later whether it deserves space.
You may discover a missing everyday layer or a pair of shoes that makes several outfits possible. Write that gap down rather than buying immediately. Try the combinations over the next week to see whether they work outside your bedroom.
Keep the personality
Your capsule can include a patterned shirt, favorite color or distinctive jacket. The aim is fewer frustrating choices, not a row of identical outfits. Keep useful pieces for special occasions separately if they are not part of the weekly rotation.
For outfit ideas, read the smart casual guide. Adapt your small rotation with the summer and winter guides. The men's wardrobe guide explains what to look for when you eventually add a lasting piece.