I ran into one twist when I got myself into Project 333, and faced the multiple motivations of wanting to think both less and more about clothes. That was the simple fact of being disappointed with what's in the stores (at least those I can afford), including the few things I did buy new (on sale, but still new) over the past year.
The website photographs are lovely; the real life garments are not. The waistband of one pair of my jeggings (four months old, wash on gentle, hang to dry) has stretched so they don't jeg anymore. The wear-with-everything blouse never fit quite the way I wanted, and it slips maddeningly out of every waistband. I can hardly believe that, like Barbie, I'm sending another bag of stuff to the thrift store. (Hers is little, mine is big.)
That brings up the old cliche about the advantage of thrift shops: that, ironically, what you're going to find there is often better quality. Like any cliche, it's not always true: any local shop is going to have a majority of clothes coming from local stores, and probably not the higher-end ones either. But if you choose carefully, the not-rayon t-shirts are there, and the wool sweaters, and so on; and that's partly because of that other old cliche about used clothes, that the ones that make it to the thrift store are the ones that held up long enough to become used clothes.
I set my change-of-season parameters for the Victoria Day weekend, about three weeks from now; where we live, that's when we start thinking "summer." Gardens go in, sandals come out. I pulled out my summer things to have a look and do a rough Project 333 count (at the same time as I was disgustedly filling the thrift store bag), and this is what I found: I am going to have No Problem At All sticking to 33 items this time, because that's about all I do have. And because every time I walk past the rayon t-shirts on the way to the grocery section, I increase my mental font another size on why I don't want to waste money on that stuff.
Which for me leaves, more or less, the thrift store.