very interesting thread, and i completely understand all of the confusion this whole concept, understanding and using it in my own wardrobe and outfits has been a big part of my style journey the last nine months or so. cake vs. frosting, veggies vs. dessert, basics vs. statement pieces......it's more complicated than it sounds!! but if you can tease apart the ideas within this concept, and find out through experiment and observation how these ideas fit into your style and lifestyle, you'll be much happier with your wardrobe and better able to focus your acquisition of new pieces.
here's a good argument for 'veggies' from Allie of Wardrobe Oxygen:
http://tinyurl.com/3ghe458
Allie also consistently argues that one woman's list will NOT work for all women at all! so, how to get started with getting your teeth into this concept? first, Aida's idea to jot down 'missing pieces' while dressing is excellent. also, if you can get in the habit of photographing your look every day (nothing fancy, just so you can see what you wore) for a month this will give you LOTS of material to analyze.
if you can't commit to every day, then DO commit to documenting any outfit you wear that you love to bits and pieces. then, sit down and really tear that look apart from the angles of proportion, fabric, print vs. solid, accessories, color - and cake vs. frosting. This will give you insight into what a statement piece is * for you * and what a basic is * for you *.
When you have a handful of 'love it, works for my lifestyle, would happily wear it everyday' looks, and know how they shake out in terms of your own statement/basic definitions, you'll have a good feel for your own ideal 'cake frosting' wardrobe ratio. Other things to consider: if that ratio changes in different areas of life (work vs. weekend - maybe more basics on the weekend?), how often various pieces need cleaning (you may want more tees so you don't have to constantly run laundry), and the effect of the changing seasons.
hope this helps!! good luck, and stick with it - some of these ideas are pretty abstract and we don't really think about our lives in this way much. it just takes time to grapple with it all and figure out how it works for you and your own situation. have fun!!! steph