G.O.
I do about 6 or 7 pants and probably 10 short sleeve shirts and 5 or 6 long sleeve. I have 3 boys in uniforms and they put holes in the pants and stain the shirts like you wouldn't believe! I made it through the year with about half of the original uniforms and bought some throughout the year to supplement.
ETA- I make it affordable to buy many uniforms with multiple kids because I am a good shopper. Yesterday, I bought 10 long sleeve polos from Crazy 8 for $53.00 shipped. A few weeks ago, I bought 10 pairs of khakis from Gymboree for around $60. I just watch sales and buy ahead. Also, you can get some better deals on non "uniform" items. A lot of stores will have a "uniform" line and then have polos/shirts/khakis mixed in with the regular line that are the exact same as the "uniform" line. The non uniform clothes go on much deeper discounts and that is what I usually buy.