I tend to buy quality over quantity. Cheaper goods often have to be replaced frequently, not to mention, they don't look as good or preform as well while you're actually using them. It depends upon the item to a small degree, but because I'm not a fan of gross materialism, I'd rather have fewer objects in my life that are of high quality, as it forces me to make smarter purchasing choices before I open my wallet and pull out my credit card. It is a thought process, not just a price thing.
Depends on the shirt. If they were just tee-shirts/v-necks then quantity definitely, I can change them up in an outfit. But other than that its always quality. A poorly made piece of clothing falls apart and tends to be unflattering when you wear it.