I have the same problem, a small upstairs balcony. As you can see I am still working on setting it up but I created a fairy garden to play in. I suggest some fragrant plants ( the small containers next to the chair are Jasmine, Lemon Balm and Peppermint). It is still a work in progress but milk crates are a great way to organize and arrange your potted plants. I am thinking about spray painting the crates in the future.
Can you use Hanging Troughs on the balcony to give you more floor space.