I have two boys, ages 10 & 11. 90% of their wardrobe consists of athletic shorts & dry fit tshirts. Both are very forgiving, size wise, and hold up well. We cold wash & line dry. For things like underwear & socks, we buy these at Costco. Kids are especially hard on socks, so we replace them quite often. We live in a moderate climate (northern California), so they each also have a couple of hoodies, and a couple of pairs of jeans or warmup pants. Jeans & warmup pants were purchased at Costco for $10/each.
Things that are expensive for them - sports uniforms & gear (although, our club typically only replaces once every 4 seasons), and shoes. They each have one pair of shoes (plus soccer cleats & slides) at any given time. We usually buy Nike shoes, as they last best & can be used for cross country practice, etc. We need to replace shoes ever 3-4 months, depending on growth & how hard on them they are.
Our shoe & clothing budget for a family of four is around $1500, and the sports uniforms were $300. So, I think we're doing well keeping the rest in check. My running shoes were another big expense in the budget, so minusing out these two higher cost items, we don't spend much.
