I bought both of my boys clothes recently...kind of over a period of a month or two but I would say my 7 year old (going to be in 2nd grade) has about 5 new pairs of nicer pants (like jeans or khakis/cargos), 2 pairs of nice sweats from Gymboree (ok for school), one sweatshirt, one jacket (the one from last year still fits), 6-8 pairs of new socks, 2 pairs of GOOD shoes that will last til he outgrows them (I swear by Stride Rite), 3-4 new short sleeved tops, and 5-6 long sleeved tops. I will buy him anything more as he needs it. Plus his bday is in November, when weather really starts getting cool/cold here and he usually gets a few pieces of clothing then too.
For my younger one I first paw through the older ones hand me downs and take inventory. I ended up getting him almost the same amount as his older brother....after about 4, kids play HARD in their clothes and they're not as good hand me downable quality.
ETA- my FAVORITE buys were from Sears last May or so....$6 Lands End jeans on clearance and $3 turtlenecks! WOW! I also got some great buys from GAP on mega-clearance, his backpack with a 25% off coupon I had for GAP, and the rest I bought with GymBucks at Gymboree. I would guess I spent about $550 for the two of them, maybe less than that, incl the shoes. Spread out over several months it doesn't seem that bad.