In my last trip to Spain, I followed Rick Steves advice and traveled light, as a result I only had a carry-on suitcase. Like La Maestra, I proceeded to leave behind all of my clothes except what I would wear the next day on flight, thus enabling me to take with me part of my purchases. The rest, primarily paper, books etc. I mailed home. But this was expensive, but well worth the bother of toting all sorts of stuff along. I also had bookstores mail my books for me, that helped.
I recently purchased a light durable canvas-durable fabric blend that unfolds into a rather large bag. I will take with me to use on my return trip for those darling shoes that I MUST buy in Spain!