I tend to go for sample books too, if I run out of a value I buy a reel. That way I only have to keep reels of the parts I use most often. For more expensive parts like many ICs I usually try to buy at least as many as the first bulk price discount on Digikey/Mouser/etc. E.g. I tend to use LT3757 switching controllers when I need to make power supplies, so buying 10 of them at $5 each is a much better deal than buying 1 at $7.50 each 10 times!