First off, I suggest buying from
www.starcitygames.com because it helps keep the lights on in here : ) Additionally, they have STELLAR customer service and they'll do everything they can to help you out and make sure things go smoothly.
If you're looking for things like commons and uncommons, then you might find some good deals on the aggregator site
www.findmagiccards.comSince some of the cards you might need are things like Golgari Thugs, asking a friend who drafts if they have any of those cards sitting around from past drafts might be a fast and easy way to get ahold of them.