Hi & welcome to HC
I would imagine the hamster you've seen is a hybrid, in most countries it's very unlikely that you would find a pure bred Campbell's or WW, it's generally best to assume they are hybrids as there's no way of knowing for sure otherwise.
Your tank is a great size, plenty of depth for lots of substrate & room for a good size house, wheel, toys, sand bath & toys. They don't generally like too much open space but you can easily fill most of the space with fun things for your hamster.
I prefer to use paper based substrate for my hamsters but I don't know if you could find that where you are, hemp is pretty good & if you can't buy a good brand locally you can order it from Zooplus, they do the
Hugro hemp which is the best of the ones I've tried.
Personally I'm not a fan of rocks in the cage, I tend to think it's a little dangerous for tiny feet, you can put something like a granite tile or an ordinary wall tile upside down maybe under the water bottle or an area they use frequently to help keep nails trim.
Things like cork tunnels or tubes make a great addition to the cage too.
Have you decided which food you are going to use? A dwarf specific mix is best & Zooplus also sell the B
unny dwarf hamster dream expert which is quite a good food for diabetes prone species.
I would avoid shop bought treats as very few are healthy & free of sugars or fruits, you can give you hamster a wide variety of natural treats like sunflower, pumpkin, hemp seeds, linseed/flax either the seeds or if you can get them the sprays on the stem, small pieces of nut are fine as an occasional treat, mine love walnut, pine nuts & monkey nuts, I usually give a monkey nut about once a week. Millet sprays are popular with Russian hams too.
Starting off slowly with a small piece every few days you can build up to giving a small piece of fresh veg daily which they love too, just avoid too many of the sweeter ones.
mealworms are a huge favourite too & make excellent taming treats as well as providing them with a little extra protein when they are young & still growing.
Hope that helps a bit, if you have any other questions just ask