The cage for your hamster should have much room. The minimum size is 50cm x 35cm. Never buy round or oval cages, because your hamster can get "crazy" in them (they lose orientation). The space between the bars should be maximum 0.5 cm for dwarf hamsters and 1 cm for syrian hamsters . When not, the hamster can leave the cage.
   In the shops we also see cages with pipes. They are very good, because in nature their ''home'' used to be in tunnels. Buy at least one SAM(TM) cage with bars, so that your hamster can breath normally and get more fresh air. The cage should have a house and a wheel. Of course there are many other articles you can buy for your little pet.