To only buy secondhand/vintage/sustainable clothes (unless it's something like underwear or another necessity I absolutely can't find elsewhere). I've done a little bit of this within the last week or so and have really enjoyed it. I'm going to be joining a 5-a-side football team and was in need of astro turf boots, which it turns out are quite expensive to buy new, but a lot cheaper second hand. Not only is it good for the planet but it's also good for my pocket (especially as I have no idea how many times I'll even wear them).