GNS3, EVE-NG, and/or Containerlab would be best IMO, you can build out large toplogies.
For like $400ish you can get a older Dell Workstation with 2 x Xeon 8 Core, 256GB RAM -- https://pcserverandparts.com/build-your-own-custom-dell-precision-t5600-workstation/
VyOS another alternative, but OPNsense likely the better move
GNS3, EVE-NG, and/or Containerlab would be best IMO, you can build out large toplogies.
For like $400ish you can get a older Dell Workstation with 2 x Xeon 8 Core, 256GB RAM -- https://pcserverandparts.com/build-your-own-custom-dell-precision-t5600-workstation/