One thing I do to keep costs down and keep life simpler is freely substitute hops varieties, especially bittering hops. You can buy a pound of some good bittering variety like Columbus or Magnum or Northern Brewer (it'll really be more like 1.5 lbs) from Hops Direct and store it in ziplock bags in your freezer.
For Pilsners and Saisons and Tripels and the like, where the flavor profile is subtle, I try to stay true to the classic hops varieties for the style. But with a rich complex grainbill (like a stout) or a beer with a lot of flavor and aroma hops (like an APA or IPA), you are definitely not going to detect the *very* slight difference in flavor from using a different bittering hop, as long as you get the IBUs right.
To make a long story short, in addition to the other good tips you've gotten, use fewer varieties of hops and buy them in larger quantities.