Dreaming of an art gallery means you are currently seeking inspiration to overcome life’s obstacles. Being in the art gallery, you are surrounded by perfection, the final creation from an artist. It can make you happy with a heighten sense of connectedness to tackle obstacles and difficulties.
If you are buying art pieces from the art gallery in the dream, then you are preparing and gathering resources to better yourself. The added extrinsic value of the dream is representative of you building intrinsic self worth in the waking hours.
But in my dream the art gallery had no art?
I would focus more on the contradiction