@coolbean @MalibuSunrise depends a lot which country do you live in and which direction does your balcony face \o/

the generic answer is "look up whatever plants are native to your area, that are evergreen or interesting in winter". for example, where I live (Germany) ericas (/callunas) ara a staple, as something flowery that endures winter just fine. if you can find a blooming Scabiosa columbaria for sale, you'll still catch the tail end of their blooming season – and so will any late-year pollinators who happen to still be flying. kale is nice if you want something to eat, as it not only survives frost but actually tastes even better after a frost. some cultivars are purple and white and basically equivalent to flowers in decorative value. some kitchen herbs are hardy enough to endure winter, like many mints and thymes. most of my balcony rosemarys died over winter but a specifically "winter-resistant" cultivar marketed as such actually worked. Helleborus blooms December–January, but in my experience is harder to keep happy in a pot. ivy (if native to were you live) is beautiful, fast-growing, and immortal.

but even plants that are used to winter can struggle on a balcony if the entire pot freezes over. in nature plants can have deep taproots to unfrozen soil, and draw water from there . in a pot they just dry.

general suggestions are:

• prefer big pots full of different plants than one little pot for each plant. the bigger and deeper the better.
• use organic fertiliser rather than chemical, avoid poison, and if possible use worm castings / worm tea. microbial life in the soil keeps it "spongy" and aerated, and helps plants survive winter in a myriad ways.
• "penguin" your pots: keep all of them bunched up close together to break the wind chill. put the larger pots and/or resistant plants (e.g. ivy, ericas) on the outside and the more sensitive ones (e.g. kitchen herbs) inside.
• mulch your pots. that is, cover the soil in a thick layer of organic material like a blanket. you can get half-decomposed tree bark on garden shops, that works well as a mulch. this helps a lot with cold, and also with moisture, drough, and lots of other issues.
• choose a corner of your balcony protected from wind and elements.
• water your plants regularly no matter how cold it is. water your pots even if all plants seemingly died and there's only soil in them.

you can also take this season to look up plants whose seeds need to overwinter, and sow them now so they come up in Spring \o/ also all the early spring bulb plants, this is when you plant the bulbs, they all work wonders for balconies: snow drops, crocus, narcissus, hyacinths, tulips, märzenbecher, and my top rec in this genre, Muscari hyacinths, are all little onions that you bury in autumn and then when you forgot about them magically break through snow to remind you spring is coming.

@coolbean @MalibuSunrise
usually you can just walk up into a garden shop and see what are they selling as hardy / Winterhart, and just ask them if it grows well in pots in a balcony.

n.b. that most sellers do not sell plants in pot sizes and soil that will last any amount of time, but in the "nursery pots" that they grew up into. you usually want to transplant them into a pot one size larger with drainage holes and fill with potting mix, then put that on a tray or underpot of some kind. failure to do so makes them very hard to water, as the nursery pot by the time you buy it is a vague sponge of root and dead dust and retains water for like 15 minutes

@MalibuSunrise I could give you plant cuttings for indoor plants, I have Begonia macolata and Streptocarpus saxorum. I'll try to winter my Oleander on the balkony because the area I live in has rarely below -5 °C