Storing doll clothing can be challenging. Especially mini doll clothes. I made a doll closet out of a modern sized jewelry box then later sold it.
If you have a jewelry box or small cupboard, you can paint and decorate it to store the smallest clothing inside.
Another idea was to make a closet out of a shoe or boot box.
Consider the plastic storage units for small beads. You may be able to use it vertically like a free standing closet. Remove unwanted bins to make longer units for hanging by clipping the plastic dividers.
Or follow my room in a box tutorial using a basic box and card board.