Signal Boosting/Acess Point

Hey guys, first time on here.

I have a router downstairs and i am soon to be purchasing an xbox360 for upstairs, i do not wish to pay for the expensive wireless adaptor, nor do i wish to have a long trailing ethernet cable.

what would i need to purchase/set up to allow me to have a wireless connection sent to a form of hub upstairs so that i can hook up my upstairs pc and xbox360 via ethernet to it and connect to the internet via it. i would also like it to boost the signal so my laptop recieves a stronger signal, although this is not necesarry.

Sorry if this is a simple question but i dont want to buy anything insufficient for the task.

Thank-you in advance