In our materialistic society, reduction should be first and foremost. Do you really need one more newly made shirt that was most likely made by underpaid workers, shipped across the Pacific Ocean, and then trekked all through a retail stores' warehousing system? Could you survive wearing one of the twenty shirts you already have hanging in your closet? Reduce.
If you must have another shirt, could you possibly find a new-to-you shirt at Goodwill or the fabulous little neighborhood consignment store? Maybe you and some of your friends could organize a sip and swap where everyone gathers to sip beverages and swap clothes that no longer fit or just don't appeal to the current owner. Reuse.
If your current shirts are in tethers, you can still donate them to many clothing donation sites. As they sort through the clothes, they'll take the unacceptable clothes, package them together, and ship them to a facility that recycles fibers to be made into new products. Recycle.
Sometimes new-to-you items are necessary. For example, you can't exactly squeeze a 18-month old toddler into the 6-month old infant romper it was wearing just a short year ago. Unless you are in direct line of a friend that has all the clothes you would ever need for your child in the fashion style you prefer, shopping for children's clothing is inevitable. I hate to shop. I do everything I can to minimize shopping. I rarely go to the mall. In recent years, I try to avoid chain stores. Thus said, every spring and fall after my son was born, I've been doing my part to reuse. I bring the clothes, shoes, toys, and anything else I can sell to the consignment sale. As a consignor, I bring my battered old laundry basket (reserved for such occasions now) and shop the night before the sale opens to the public. In 2-1/2 hours time (an hour is spent waiting in line to pay), I get almost everything my child will need to wear for the next season at a steal of deal.