Also, if the randomization bugs you, you can buy singles from numerous online retailers and some FLGS's. There is a list on Maxminis somewhere, but I generally buy from popularcollections.com or colossalgames.com. The commons and uncommons are really cheap and plentiful. Commons about 50 cents, uncommons usually about a buck. A 20 figure Orc army? Probably put one together for about $10 buying singles, including shipping.
'Course, it's the rares that get you, but even most of those are less than $12 each. Some of them are just too cool to pass up. Just resist the temptation to "collect 'em all". Once you cross that line, you are talking serious fund hemorrhage. Even then, you need to buy singles and/or trade to do that cost-effectively. Only great fools with no concept of probability or pot loads of cash will try to collect every figure just by buying boosters.