Great post!
I do not have a firm strategy but probably elements of
Outfit Lineup - I often repeat outfits and tend to have a statement piece I can only wear with one other thing (often jeans). I will then usually wear the same footwear.
Trend Update - yes I do try and keep abreast and bring in new shapes or new to me pieces. In 2014 it was two pairs of patterned trousers, draped asymmetric hems, and several sheer pieces (or sheer in part).
What I am thinking about is the French system of a certain number of pieces per season. Last year I added 23 items to the wardrobe (excluding exercise gear, underwear, socks and accessories) but including footwear and handbags. This probably feels about right to me. So I am going to aim for 15-20 over the whole year including bags and footwear. To keep within budget I will thrift some pieces as I want to make sure some of them are genuine quality. This will be a challenge as I do have some gaps due to wear and tear. I am also trying to think about the power of one - one pair of great work classic trousers, one black blazer etc...This does not work for all categories/capsules but works well for others. For example I had a longing for a new swimsuit on holiday. I have one lovely swimsuit, and one practical swimming suit for doing lengths/boogie boarding etc. Since they dry in about 30 minutes I do not need another one. I will wait until one perishes and then replace.
I have some way to go though!