I did a couple things. I bought some bins with lids that had handles on them. They are big enough to store quite a few items and small enough the kids are able to carry them around. (Think like the size of a portable file case. I bought like 4 of them. I put all of the my little ponies in one, small dolls in another, puzzles/magnetic dolls in another, and then I had barbies & clothes in another. If we had a lot of blocks, I would put them in one of these cases also. The nice thing about these cases is the kids can bring them out to the living room, play with the toys, then pick them up and take them back to the playroom.
But over Christmas my daughter got a ton more barbies & barbie clothes. I was going to buy one of those rolling barbie cases but my SIL gave me the idea of buying one of those hard case luggage on rollers, and this works perfectly. In the big part my daughter puts all her barbies. Then it has a zipper pouch where she puts all of barbies clothes & accessories. She even has her brat and moxie girls in there.
Oh and we have a lot of dress up clothing. I just bought a rolling laundry basket that has handles and now we shove all the clothes in there. I'm going to put the necklaces, purses, etc. in one of the carrying tubs with handles.