We live in a world in which there are so many things one could buy! How do you choose which ones?

The jeans, or the sweater? The sweater in your favorite shade of blue, or a wild card red? Maybe jeans and a sweater both, but hold off on a new pair of boots?

With the turning of the calendar to August I am starting to think about autumn wardrobe planning, and one thing I think is that I am not always very effective at prioritizing wardrobe purchases. I am wondering what rubrics, systems, or thought processes others have.

Two things that I think pose a challenge for me in this department:
-I shop mostly online secondhand. So, potential purchases for me are not seasonally restricted the way they are for people who shop retail. (Do I buy the skirt that will be the perfect thing next spring, or the nice but humdrum sweater that will be useful next month?)
-I have a quirky style that is not trend-driven. So, in theory I could make a list of, say, the top 5 items that would make my wardrobe better, but it could take YEARS for those items to show up. What should I buy in the meantime?

If you have thoughts about dealing with those two specific challenges, I am happy to hear them. Mostly, though, I am just on a data-point-gathering mission here, and am interested in how *you* prioritize purchasing decisions in your own wardrobe.