Debbie - I think one of the realisations for me of this thread is that to create a great wardrobe plan you really have to know yourself. Some plans work for layers, some don't (the 5-dress SWAP comes to mind). Some plans work for hot climates, some don't. Some plans work for the city, some for the country, some for the chic, some for the romantic, etc. A successful wardrobe plan to my mind has to match its wearer: in terms of colour, in terms of style, in terms of location, in terms of season, and in terms of body shape. And this is why so many fail, especially the "10 garments you must own" type - I think everyone's list is quite individual. Probably those based initially on your closet (or laundry basket) are the best bet. That said, it's always fun to read someone else's list.
Here is my list of the 10 ESSENTIAL garments (for me) to own:
1. Casual trousers. I live in jeans-styled trousers of one kind or another; they are absolutely indispensible to me. I want six pairs. Six, do you hear me? But I can get by with two pair.
2. Camisoles. I am a) very cold, and b) like gauzy shirts. If I could have only one, it would be flesh-coloured. If two, the second one would be blue.
3. T-shirts, both short and long-sleeved. For me, in creams and blues.
4. A great woven shirt. Good for layers. Ideally, at least one plain and one fancy. Colours? Blue and pink.
5. A waistcoat/vest. Did I mention I'm always freezing? Colours? Neutral.
6. A cardigan sweater. Ideally one light, one heavy wool. Colours? Neutral.
7. A great skirt suit. For random special occasions where one needs to look sharp. Skirt and jacket should be wearable separately. Colours? Dark neutral (black)
8. A great dress and matching wrap or jacket or something. For going out. You know, once a year.

(Colour? I dunno - sparkly? whatever)
9. A light coat. (Colour: Neutral)
10. A heavy coat. (Colour: netural)
In other words, colour only in shirts, LOL.