Gallery Organizer provides a two level hierarchy for organizing photos. There is a logical folder > sub - folder organization. Get started by creating collections (categories) each of which can have many user defined albums containing images. One can also search for images by name for instant access.
It is free of cost, ad free, super fast, lightweight (1.14 MB only). One of its kind app in the play store to offer two level hierarchical organization. Very fast search image by name feature that is present in only a few apps currently. Easy to use UI.