There is a book titled "Container Gardening for Dummies". You might be able to source a copy through your library or second hand via E-Bay.

Pity I didn't have a copy when I had a 3rd floor, west facing balcony in Sydney. Even the garden gnome died of thirst! I put it all down to gravity and the scientific need for the water to reach ground level.

I'm certainly no balcony gardening expert but I would recommend pot plant saucers, water holding crystals in your potting mix, and mulch.

The precise recommended water "dosage" might be a bit difficult to adhere to. The requirements of the Dracaenae are going to depend on what it uses up itself and how much evaporates - and this depends on growth, daily climatic conditions, etc. Also depends on the type of pot - eg, terracotta which allows water to evaporate through the sides. I'd aim to keep the potting mix moist and, yes, check the moisture beneath the top of the mix. The Dracaenae would also probably appreciate regular spraying of their foliage - pick up a cheap spray bottle from your local dollar shop.

The yucca, a desert dweller, is incredibly drought hardy and would need very little water. The problem is that once pot plants dry out, they can be extremely difficult to "wet". I'd water more often than once per month, but only use small amounts of water.

If your pots do dry out completely, water them by immersing the whole pot in a larger container of water (laundry tub if your pots are large) and leave to soak for a couple of hours.

Another observation - balcony plants seem to be happier in the close company of friends. Position your pots in a group.

Thanks for the advice. I repotted the smaller Dracaenae last weekend, so fingers crossed they'll survive the move.