Both. There are certain things that I see that I like to buy, such as mirrors, side tables and decorative shelves that are really out of my league to make. I alos like buying figurines that match my decor.
However, I enjoy making the majority of my accessories: curtains, pillows, runners, doilies, candles, cushions, potholders, rugs, place mats, tablecloths and art prints just to name a few.
I also like to, as you say, up-cycle other items. Many of the purchased items i mentioned above are things I can find in dollar stores, thrifts stores, and yard sales. I can then repaint them to personalize them to the room.
There is an amazing variety of stuff out there that can be turned into something unique: picture frames, tables, stools, wooden chairs, vases, bowls, baskets, and so forth. It doesn't even require a lot of crafting ability; most things can be recreated simply with a can of spray paint.