Please read these blog posts by FiveLittleHams:
Provide hamsters with foraging opportunities, ratrations.co.uk sell the Pick n Fly pack and the Harvest Festival pack, they also sell various millet sprays. Your local pet supply shop might also sell some of these things, they'll probably be in the bird section. Getzoo has a wide variety of different sprays too
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!
Roborovskis need a large sand area, not just a small bowl!
Provide your hamster with various substrates, coco soil is a fun texture to dig in! You can buy it in blocks in reptile sections of shops