Where to start!
cage wise, I would go with any of the following:
Ferplast Kios (7mm bars)
Gabber Rex or Zoozone 1 (both similar in size)
Some members would happily keep a single Chinese in a Ferplast Duna and there`s nothing wrong with that, But I suppose you need to look at all aspects of what will be in the cage or whether the hamster you get prefers the smaller cage.
The first three would probably be the maximum size for a Chinese due to the fact that they allow for decent floor space, yet are not TOO big so as they don`t make the hamster wary or nervous. Unless of course you get one that has an extrovert character!
Diet would consist of a decent hamster mix like Burgess Supahamster or one of the JR Farms ones if you prefer to shop online. Don`t worry about the corn or peas in mixes as these are essentially a part of the nutrition. It`s added sugars you need to be aware of like treats. Chinese hamsters are fine with treats from natural sources like bits of mealworm, a small amount of millet from your flat hand, a few sunflower seeds/hemp seeds.
Fresh raw veg is also enjoyed but only a few times a week in fingernail portions. A little cooked fresh brown rice.
DON`Ts: There are none really although Chinese hamster`s don`t seek out open spaces well and will lie flat and become a little unsure. They much prefer a sleeve to run up or hide inside some old fleece or hide in your clothing! So they don`t require balls or floor time as such, but once settled, they do enjoy short play sessions on their terms.
Smell....they do have a scent but nothing really pungent. Just much the same as you might get from other dwarf hamsters really.
Think mouse without the long tail and you have a Chinese hamster.
They love to climb, but height kills, so not in a cage that allows the hamster to get carried away.