I have a bonsai of Euc. gunnii, Euc. pauciflora, Euc. camaldulensis and Euc. nivalis. The mallee gums are fairly easy to bonsai, but you need to be very confident about their cultural requirements. Australian plants also have very different structure to the traditional bonsai forms, and really you need to study them in some detail to make convincing specimins. Finally, many Australian trees require deep roots - the standard bonsai pots tend to make the plants very fragile and they die readily.

You can not propagate Eucs by cuttings or layerings, seed only. (This isn't entirely true, but practically it is)

You can limit its size by keeping it in a smaller pot, and pruning if necessary. It will overwinter nicely in a garage with adequate light. It doesn't need to be full sunlight; light from a window nearby will do. Don't water as much during the winter, just enough to keep the soil from drying out completely.

Here is a link that might be useful: ficus benjamina bonsai