I can help as I was like you and wanted a complete set!

you need quite a few stuff and it can be costly but with enough hunting around, you can find some deals!
You will need:
Namco System Super 256 (the only system that can run TC4 unless you have the patched HDD file made for the normal 256)
Namco V329 NA-JV I/O pcb. I haven’t tested if other versions work but the FCA2 I/O pcb that Cobra the Arcade used also works.
OMC-GZH200 Gun/IR led I/O pcb.
And the 10 IR LED pcbs, the complete gun assembly and the wiring. I had to do the wiring my self and it was a pain in the ass lmao! The arcade pdf manual is online and I recommend you follow the Standard cabinet manual as the Deluxe version is a bit hard to understand the schematic.
Don’t forget the power supplies! One for the arcade system, I/O pcbs and one for the 24v recoil if you want that feature.
If you want a 2 player setup, you’ll need the exact same parts as player one. They don’t share the same system or I/O boards. They are separate.
You also can not use a gun and IR LED PCBS from a different game like HOD or any other SEGA gun game with a similar setup. The only game that has a cross compatible setup with TC4 is Cobra the Arcade. Light gun I/O pcbs won’t work with the game either.