First choice would be to contact a neighbour and pay them a tenner per month for their broadband password as a stop-gap. That is most likely to get you a better signal and would avoid having to purchase a repeater which likely wouldn't work well because 1 bar is subject to too much interference.
You want to amplify a 1 bar signal?
You can't see a neighbours Wifi instead?
First choice would be to contact a neighbour and pay them a tenner per month for their broadband password as a stop-gap. That is most likely to get you a better signal and would avoid having to purchase a repeater which likely wouldn't work well because 1 bar is subject to too much interference.