If you only want to get the basics (minimal equipment), get a good computer for around $3000, the Vanishing Point Vector Lite System for around 5000 British Pounds, you can use your DSLR or Mirrorless Camera with HDMI out. And then you only need some cables, adapters, tripod and a greenscreen. That way you should be good for around $10000.
But more is always better... 🙂
Some people say "start with a vive tracker", but I disagree!
The vive tracker won't make you happy and you won't be able upgrade it to a professional solution.
The cheapest professional solution is the Vanishing Point Vector lite system. You can upgrade it even with 2 x Vanishing Point Viper Sensors for Focus & Zoom tracking and will get you a perfect composite (no sliding). You won't need anything else.
But the vive tracker will soon be in the corner. And if you got 4 base stations and 2 tracker like me, this is $1200 lying unused in the corner... 🙁