Answer: First off, containers and especially large ones full of damp soil can be extremely heavy so you should check with your building management about weight restrictions. Secondly, you may find that your terrace is very windy. If this is the case you may need to erect wind breaks and/or water extra often, perhaps as often as twice a day. Finally, since your terrace is so very shady you are a bit limited in your plant selection.
The following plants would do well outdoors for the summer. You might consider the various types of impatiens and tuberous begonias for blooms, coleus, caladium and hippoestes for brightly colored foliage (one of these may be what you saw at your neighbor's), and perhaps a small-leafed or variegated form of English ivy along with asparagus fern and other types of traditional houseplants such as philodendrons for more textural contrasts. The ivy could climb as well as be trained into toparies for added interest. You can certainly hang the containers or set them up on supports to increase the visual height of the plantings. Unfortunately I can't think of a flowering vine that would do at all well in so much shade.
All of the above plants should do well in containers with a minimum of care, meaning regular watering and fertilizing with a water soluble fertilizer, along with occasional grooming or removal of any damaged leaves and so on. For general care instructions and more plant suggestions you might consider a basic reference book on container gardening. One I particularly like is Container Gardening for Dummies by Bill Marken, ISBN 0-7645-5057-8. which looks at all types of plants suited to outdoor containers.
With regard to year-round interest, I can't think of any thing for you that would thrive in a container outdoors and bloom in the winter. Further, most of the early blooming deciduous shrubs and trees that might possibly survive the winter in a container would probably require a larger container than a five gallon bucket as well as need more sunlight. Unfortunately too, most smaller evergreens such as boxwoods that might survive in a smaller container would also require more sun than your plants will receive. For that reason I would suggest training English ivy onto vertical topiary frames in geometric shapes such as cones or balls to provide "something" to look at outdoors all winter. You could also bring many of the other plants I suggested indoors to enjoy in a sunny window.
Good luck with your project!
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