If it`s your first time keeping a Russian dwarf, I would say start with a single hamster, preferably one that is looking for a home already. And unless the hamster is bought from a registered breeder (by registered, I mean a breeder who shows hamsters and is well known in hamster circles) not just someone who breeds and advertises. Most Russian dwarf hamsters are hybrids these days and not pure winter whites or Campbells.
I personally feel that the Mini Duna is the bare minimum for a dwarf hamster, but it`s not the end of the world either. Tank style cages the size of the Zoozone 1 are better because they give that little more floor space and you could still add a shelf inside. What you need to remember is, even dwarf hamsters have lots of energy to burn, so giving one as much room as you can is the way to begin. But using a Duna as a taming cage for a wee while and then moving up to the larger tank is also a good idea.
Hamsters in general enjoy human company, but when it`s on their terms. Meaning, don`t wake your hamster up to play with him/her as they could become stressed and nervous and start to bite as a consequence, especially while inside their cage as some can become cage territorial, but that`s nothing to worry about because many dwarf hamsters can be like this, but fine once being gently handled.