A saiga for clays... You're a pioneer. I'm not sure if any of the stock barrels from saiga are threaded for chokes. That being said I know nothing about their shotguns. Choke tubes are used to adjust your shot pattern. What I'd guess you have right now is just nothing at all - a plain .730" diameter all the way through, possibly with no female threads inside your barrel that would allow for chokes. This would be referred to as a cylinder choke if you installed one with the same specs. After that comes improved cylinder, light modified, modified, improved modified, full, and turkey. Cylinder does nothing for your pattern and turkey chokes are typically the tightest patterning chokes you'll find.
For skeet, most people don't go very tight at all because the open pattern allows a little room for error. You might would want to tighten up if you started doing trap.