Syrian hamsters need at least a 28cm wheel, like the Trixie one. They're good climbers so benefit from the height of the cage being filled with hammocks and bridges etc.
Dwarf hamsters need at least 20cm wheel (though smaller dwarfs like robos can sometimes have a slightly smaller one such as the medium sized silent spinner) They aren't as good at climbing as Syrians so they do best with lots of ground-level tunnels and dens.
Syrian hamster toys:
Dwarf hamster toys:
Example of a brilliant set up using an IKEA Detolf:
These photos are from @dogshamsters on Instagram. This is the sort of habitat that we believe everyone should aim to create for their hamster. If you're starting out with one of the minimum sized set-ups then please consider potentially upgrading when the opportunity arises. Keep an eye on 2nd hand sites for nice sized tanks or repurpose furniture into a DIY cage. All hamsters deserve to live like this!