Begonia bogneri is an unusual but not overly difficult species. It is a small plant, and is tuberous - although it doesnt need a dormancy. The only time I've seen any go dormant is if dried out or otherwise stressed - at which time they can shed leaves. However, even if they do - they usually just pop back to life once given a two to four week rest and then with careful resumption of watering.
My mother plant sits in a covered 8" glass bubble on a diffusely lighted windowsill at a minimum 60F. I appears to not need a dormancy at all if kept warm and moist. I grow it in a small net pot which raises the crown above the level of the surrounding moss / medium in its glass bowl - so far its been problem free. Even so, this is probably not a beginner plant.
Offered here are fully established and well rooted plants in 2" pot.
More detailed info Here
View Terrarium / Begonia Culture Sheet
|Int - Warm||Low - Medium|