Same kids, for larger items I was able to get stuff cheap at yard sales.
For DD two years ago, I had Walmart and Amazon registries. Amazon gave me 20% off most of what was left on my registry as my due date got closer, and that helped a lot.
It's been about 8-10 years, but I used to buy clothes for my niece and nephew in bulk on eBay. It'd end up being $0.25-$0.50/item if I was persistent, and most of it was EUC or NWT.