Buy a plastic easy to clean cage with round edges on the inside so that it's safer and even easier to clean. I recommend Habitrail OVO Suite.
One hamster per cage, please. Hamsters are solitary animals. Try not to pair them unless you really know what you're doing.
When bringing her home, be careful not to shake the box too much. Quickly assemble and get her new home ready. If possible, put in a little bit of the original bedding from her old cage at the pet store to help her feel secure.
I found a really good bedding. Ground walnut chips! They're not dusty (which I really hate in other types of bedding), and they last longer. Ours last almost two weeks before we need to change it.
Hamsters want a quiet safe corner to sleep. Put some light bedding in her room. I use the shredded paper variety (store-bought).
Never wake a sleeping hamster. Leave them alone if they are not in the mood to play.
To familiarize her with you, just put a piece of sunflower seed on your palm then put your hand gently in her cage. Let her climb into your hand voluntarily. Never grab at them. Never speak too loudly. They are easily startled if you do. I guess it's hard being a really small animal.
Do not buy cheap hamster food that looks colorful but not natural. Buy one that contains lots of oats, some sunflower seeds and corn. Just buy one mixed bag is enough. They don't really need much treats. But buy them some pieces of wood like apple orchard chips or branch. They love to sharpen their teeth on those.
If your tap water is not drinkable, better fill their bottle with boiled water or mineral water.