I have a monthly clothing budget, but I do tend to think of shopping by season too.
We have four distinct seasons here, but Fall and Spring are the two biggest clothes-shopping seasons in my mind. Fall because that's typically when the major new fashion trends come out, and when I'm in the malls anyway helping the girls shop for their back-to-school wardrobes. And Spring because by that time, after a long winter, I'm desperate for a change!!
Also those two seasons tend to be trickier to dress for, because the weather can be fickle, changing from warm to cold often during the same day.
Winter - it's important to add a warm coat and boots, hats, scarves, mittens... and possibly a new holiday dress.... but for the most part, the items bought in the Fall can be "winterized" ...
Summer - not so much, because our summers, while they can be quite hot, tend to be quite short (July, August). We spend our weekends lounging on the beach, lakefront, or out on the river in our boats, so having tons of fancy clothes for this season is just not a necessity. I also don't like to spend that much $ on summer clothes because I find that you sweat so much in them, they don't last as long.
I never kept a list until YLF. By that, I mean a wish-list of items I wanted to add. I would just add willy-nilly without too much of a plan. I have long kept lists of clothes in my closet. I started that in high school. I was not very fashionable - more of a wannabe - but I did use to make lists of outfit combinations back then. I have always been a list-maker.
I'll add to this that I also use any vacation trips as an occasion for major wardrobe purchases. I guess, without realizing it, I have been practicing "capsule" wardrobing for awhile. I love the challenge of a trip because it forces me to buy items that all coordinate together and fit in one suitcase!!!
I am hoping this summer to not buy too much more. I got my silver flats and second pair of clam diggers which were my most important items to add. Not as important - refresh my black and white cardigans (I could probably get by without this), and find a perfect pair of white denim clams (not holding my breathe - but if I find them, I will snap them up). Otherwise, I expect I will focus my July/August wardrobe on the pieces I packed in my suitcase and wore in Paris last summer.
If I can minimize spending for the summer, then I will have more to spend in the Fall.