I have never had luck before; they always rotted. I concluded from reading that I was putting them into too large a pot & they couldn't handle the moisture. Does that sound right?

I decided to try again when I came across tubers deeply discounted on spring clearance. I bought begonia pendula, begonia 'Odorosa', 'Non-Stop' and tuberosa 'Samba'. Put them in commercial potting mix, but this time also put them into the smallest containers that they could fit into.

So far so good, some have leaves, some are just sprouting, but none lost so far.

So now I want to move the leafed out ones into larger containers and this is where I am unsure about how to proceed.

1) How large should I go? another intermediate size, or can I put several into one that will be their home? How many into what size?

2) I have pretty glazed pottery (I was successful in overwintering a full grown begonia in one of those last year), standard terra cotta, and also those coir-lined baskets. Of course, plastic too. Is one of those preferred, or some equally fine? Which would you choose?

Thanks for any hand holding!