Honestly, when I buy a new rifle and figure out what it likes to eat, I buy enought bullets, primers and powder to burn out the barrel. With my 7WSM I figured on 1,200-1,500 rounds and bought 3,500 Berger 180s (I got two barrels right off the bat). With a .308 that amounts to a bunch of bullets and a ton of powder, so I only buy a year or so worth (figure 1,500 rounds a year) storage is a bit tough where I'm at.
With some rarer commodities, like Federal 215M primers, I bought 1,500, but then I saw how hard they were to find and recently bought 6K more when I saw someone that had them. Buy in bulk, as the prices NEVER seem to go down and they gain in value sitting in your store room. Cost is always a consideration and your ability to properly store the items. Bullets need no temperature control or special storage so they are easy.
fyi - If I were to sell my 7mm Berger 180s for their current retail price I would make at least $6.00 a box, depending upon the retailer.
JeffVN