For development or just playing around, you can run it in a virtual machine.

Do you know if I can reliably use a compatible usb WiFi adapter with a vm?

It is hard to fully generalize that question, since I'm sure it varies a little bit depending on the virtualization software and how well it passes through USB devices. I don't see why it wouldn't work, though.

AR9331 is well supported and dirt cheap.

Router like TP-Link WR-741 is good one.

I found routers on local classifieds for $5.

pcengines apu2 should be good for hacking. Very open platform (it runs coreboot). Not very cheap though.