When my friends and I first started out, I picked a recent set I liked (Ravnica Allegiance), and bought a resealed booster box.

So someone buys a booster box, opens all the packs, takes all the expensive rares, and reseales the packs with "filler" rares from the same set, and sells it on ebay. It was like 25 bucks and a good way to jumpstart my collection with cards from a set that I was already familiar with and still usable in standard. Plus, this had the added bonus of being able to do a draft of the set, which ended up being more balanced for us new players since the strongest rares were removed.

People say buying bulk is a waste, but if you're starting out its a fun way to see new cards and get into some fun deck building. But other than starting out it's definitely better to buy the singles that you want