I had different columns for different things, so tops, trousers, skirts, dresses, jackets etc. I listed everything I had that fitted me: black long sleeve top, white shirt, navy/white stripe blouse etc.
Then I made another list of things I needed, in order of priority. So for example I had lots of black tops and three pairs of jeans, but no black tailored trousers, which I like to have for work. So that was my top priority. I also needed some summer clothes, so I added a few things to the list e.g. white tank top, navy linen trousers etc. I had a column for how much I was willing to spend on each item, and a column of how much I actually spent, so that I could track my budget.
And then I just worked my way through the list of things I needed in order of priority and searched eBay. Once I bought them I moved them on the spreadsheet to the list of things I have.
My wardrobe is fairly boring and minimalist but it works well for me. Most things go with most other things, which is useful because I’m not a morning person and don’t have the patience to plan outfits every day.
There might be better ways to organise a spreadsheet, but my way was fairly quick and easy for me. (I also used colour coding, but it’s not really necessary. I just like a bit of colour in my spreadsheets.)