Hi have a question, I live in a three level townhouse, the router is on the ground...

[Josh Must]

Hi have a question, I live in a three level townhouse, the router is on the ground floor, which is fine for my computers since they are down there. I am looking for a repeater for the second and/or 3rd floor. I honestly have no idea what I am looking for, any suggestions would be helpful, trying to stay under $100, thanks!