I know fu** all about sustainable fashion and what you might possibly need for that, but if you're looking into business I'd go for Maths, English Lang and the Sciences as your indispensable subjects. If you need to choose more I'd also go for Chinese, Geography, Economics and/or English Lit if you like (although do bare in mind that you don't need economics igcse to get into economics as, at least up to my knowledge). The rest probably won't help you much in so far as business is concerned.