One poster did it with plastic pipes from the Home Store. No glue, they just push together.
One caution with that. Light, airy and comfortable duvets/quilts don't make particularly good soundproofing. Heavy is good.
Exactly. Do the short form stuff right away and save the long-form book (if possible) for better kit. I'm a believer in hanging on with white knuckles if you get something working.In the meantime if you can get work out the door using the mosquito killer plugins go for it.
If you do get better equipment, you may find the Mastering different. If you cast off the USB microphone, you won't need Mosquito-Killer any more. If you get rid of that background noise (the hiss, not the whine) you may not need quite as much Noise Reduction, etc.
Two makers have native mono, voice compliant interfaces. Behringer has the UM2 and the UMC22, and Focusrite has their Scarlett Solo.
The microphone is up to you. Asking about the microphone is like asking someone what kind of music they like. Get one of the interfaces first and then see if you can borrow a microphone. Do you know anybody in a band? Well enough to borrow a microphone?
You should know that although USB microphones are limited by the length of the USB cable (6', 2M) an XLR microphone cable can be extended to 75 feet, 100 feet or more. If you're not paying attention to the Audacity recording meters now, you can push the interface and computer out of the room.