I do two things: drop a lot of stuff off and then browse for deals, which are everywhere. Amazing at Goodwill and "Vintage Value" here if you look.
The last few years have been a bit of a reckoning for us: We have lived here 26 years and, while we are good about our footprint, accumulation by default is real.
So I have been donating like you read about, judicious about buying unless it is a smoking bargain..
When the kids were little we rolled stock every year: donated baby stuff, looked for toddler stuff; donated toddler stuff, looked for...why buy stuff new when they will wear it for a year before they outgrow it?
Now, with the kids gone, we are making sure they purge their stuff from the house (clothes, books, just stuff) and either take it with them or donate it. I made two trips last week with Arden and then found two pairs of shorts, perfect condition, for $5.00.
I go to farm auctions, sell and rarely buy, volunteer at HFH (much less of a deal in our area) and generally look for what I need used.
The next few years I am going to auction off a lot of farm equipment, mostly support gear.