I'm kind of picky. i have gone through some second hand stores with DD, but perhaps since it was a consignment store, the prices weren't any cheaper than buying new stuff from Carter's when it hit the 50% off and I had my 20% of coupon. I found I could get an entire season's wardrobe for around $50. Heck, using their sale after Christmas, I got 37 articles of clothing for DS (4 months) and DD (almost 4) for spring and summer (for her since I think he'll grow out of his clothes before then) for $127. and that was taking into account DS would need both long and short sleeve clothes since winter hangs on here.
We do have a thrift store, but seeing as I'm picky, I didn't care for a lot of what's there. a lot of character clothes because that's what they sell a lot of in the PX - which is why i was thrilled to see that Carter's finally opened up a web shop. When we first moved, I had my mom bring some clothes for DD that first winter and MIL loves to send her stuff, which is generally stuff I would have bought. and even if I did go straight with the character stuff, there's generally not enough for a wardrobe there at any given time.
We're not on post now, so it's hard to connect with the other moms, but I would be inclined to not take the hand me downs to let them be offered to another family of lesser means. I have donated all the kids' clothes to the thrift shop. We did offer DS's clothes to another family, but they weren't interested.
For DS, I won't buy anything full price because he does grow out of it so fast. The big shopping spree above, everything but one really cute shirt for her was from 50-65% off. That cute shirt was 40% off. Even for her i don't like spending full price, though I did get her a t-shirt the other day, but PX prices are slightly discounted.