Since you are having Wifi connectivity issues from your PC and not other devices, using a USB Wifi Dongle may make a difference. However, you may want to change the Wifi channel on the router, first. Sometimes, interference from the router's coverage zone can cause connectivity issues. The Wifi channels you can use are 1, 6 and 11. If changing the Wifi channel solves the Wifi connection issue from your PC, a dongle will not be needed.
My Internet connection is getting spotty - brief interruptions during streaming, web pages first show as "not available" but eventually show up, email client often can't reach the server, etc. - but other devices on the same router do not show the same symptoms. I suspect my onboard Ethernet adapter is going south. Can I bypass it with an external USB wi-fi dongle, or would that also be dependent on my network adapter? Thanks for your help!