This is one of my favorite money-saving things, finding well-priced, quality children's clothing. Here is what I do:
Trade clothes with a friend/family member
Buy gently used clothing at consignment stores, thrift stores or garage sales
Buy clothing on super-clearance in the next larger size at end of season sales
Hand-me downs from older to younger siblings
I just did all of the above in the last 2 weeks. I do like to find things at garage sales for 25-50 cents but I have not had the best luck lately, probably because I haven't had the time to spend going to garage sales. That's why the "trading" with friends works so well. I get to look through their clothing and they do the same thing with my children's clothing. No money exchanges hands and after we outgrow the clothing, we give it back (and then I can sell my kids clothes if I want). I shopped some clearance sales last spring and have some brand new jeans that were very well-priced.
We have full drawers and closets for fall and winter. I have winter coats, hats, mittens, gloves and boots and spent $2 on my daughter's boots and that was it. Everything else was from hand-me downs or trading with friends. Same with the basics of jeans, sweat pants, long-sleeved Tshirts and sweaters. We even have some nice dress pants and shirts for the boys and some beautiful dresses for my daughter.
We are set for this fall and winter. But as you know, children grow and growth spurts aren't on a schedule! So having things on hand in the next size is always good at our house. Plus, boys can be so hard on clothes, especially the knees of favorite pants or jeans. So while I am "done" with my back-to-school shopping, I will still keep an eye out for sales or even trade clothes again at Christmas time so the kids have some larger and new-to-them items.