First of all, you need a good sized cage.

Then a water bottle.

A bowl and food (I suggest pellets, as they are better for their dietary needs, as when they have mixed food, they pick out the bits they like and don't get the full nutrients).

A wheel.

Any homemade toys, like toilet rolls.

Or shop bought toys, like this tunnel see saw.

Then they need wood pulp or another type of hamster friendly wood to have on their floor of the cage.

Then bedding.

And a little hut where they can hide or sleep in (put the bedding in this).

Lastly, a hamster ;D this is my baby Theodore :)