There are Wireshark forums that you can post to about adapters that work or not. If you buy one, be sure it's a model that folk have tested.
That aside, there isn't much reason for most to run this app. I trouble shoot networks all the time and never needed this.
Ok so I got wireshark and I want to use moniter mode... which I think is the same as promiscuous mode, i dont know. But my laptop apparantly can't do it. If I was to buy a usb wifi adapter would that help?