Do you want vegetables or flowers? How much sun do you have? You can start a 2nd crop of tomatoes - grape tomatoes would be good in a pot, as well as peppers.

For flowers.....you might start anticipating fall colors - make a big pot w/ several different kinds of flowers and plants - tall purple fountain grass, trailing chartruse potato vine[which can trail along your balcony rail], profusion zinnias, periwinkles, angelonia, coleus. Go to your local nursery or Lowes/Home Depot to see the many kinds of flowering plants available.

I do grow seeds but have a farm and plenty of land, but since you have a balcony, opt for instant gratification and get annuals in pots.

If your balcony is shaded, you might look at ferns, impatiens. For sun, a potted hibiscus blooms alot and has pretty folliage. You have lots of options and am sure others will reply, so if you have questions, be sure and ask. There are many plants that you can use to have a balcony full of plants that will be entertaining and gratifying.

You might get really good results if you get the lightweight pots that just look like ceramic or concrete, so you can more easily move them around to take best advantage of your sun exposure. Be sure to check out the plant tags to make sure you are giving them the correct light. Expect to water every day, especially if your balcony is in bright sun and/or you use actual terra cotta pots. Those are the basic orange clay ones you see so much and they're very porous.

Finally, if you want to mix items in your pots, make sure you group them with the same light and water requirements. Mix the heights and consider using one plant that has a trailing habit to spill over the side, along with taller or more compact varieties. Have fun and ask as much as you need to, on here. This is an active and friendly forum.