Wireless N options on Mac Mini 2007

Hello all, I recently pulled an old mac mini 2007 A1176 with OS X 7.5 lion. I was planning to set it up to be my file server and just plug all my external hard drives into it. I used parts I had and upgraded the RAM to 4 GBS and put in a small SSD to keep the thing quiet but then after getting it set up I forgot the fastest connection is a g. I know I can upgrade to an airport extreme to get N speeds but now I am thinking I should just get a USB wireless adapter. Do the 15 to 30 dollar usb adaptors work ok for 10.7.5? Or can I even use AC? I feel like this might be a better way to go incase I decide to ditch the mac mini for something else.

Thanks for the advice

Well being eleven years old, it only has a b/g card fitted. USB dongles do not co-operate very well with Macs, particularly pre 2012 models.

Do you have a central router that has an Ethernet LAN port? If so, can you just connect the Mini by cable to that router and attach to the network that way? Speeds will them be throttled by the clients, not the server, which would be at the wired speeds.