I was doing a bit of research on this i came across interesting articles based on how to built your own NETWORK FIREWALL.
You will need these,
A suitable PC, with a CD-ROM and USB port - we suggest a Pentium II
At least two Ethernet ports (onboard + a second card or similar)
A blank CD-R to burn the system CD
USB thumb drive, floppy disk or hard drive.
For more details,
https://www.engadget.com/2006/05/30/how-to-build-your-own-network-firewall/
https://top10league.com/best-wifi-card-for-pc/

Cisco Certified Network, Level 5 Engineer.