In a perfect world, I would love to have my clothing come from many different places. But the truth is, I am hard to fit, and I am very particular about things being just right style-wise. So I do rely on a handful of retailers to get items that feel like "me" (Anthro, WHBM, Topshop, Free People).
But when I start feeling bored, then I know it's time to start digging around in other places. Shopping at large department stores can be helpful because they carry so many different brands, and I can easily search by size. This helps me expand my selection of brands in a more painless way.
I wouldn't recommend getting huge amounts of clothing from a single line because our style can change. And if that happens, you will be stuck with a bunch of clothing that you don't enjoy. I would buy maybe several pieces over some months and then see how you're liking them. You might find that your style changes slightly as you wear the items, in which case you may want to start looking elsewhere for what is tickling your fancy.