Depends on what you want to pay. If you want the "best" then you will pay a lot of money for no reason. If you are using it for documents only then a 3 in 1 from Epson or HP at around £70-100 will be perfectly satisfactory. I have an HP Officejet 6700e which cost me around £65 on eBay and it works perfectly.
Best phone camera 2017