Greetings JOHNACM and welcome aboard
The Winchester 97 is a modern (smokeless powder) shotgun. Some older, unaltered, Winchester shotguns may have short chambers. Before you shoot yours, have the chamber length verified -- there's a very small chance that it may not be suitable for standard 2 3/4-inch shells (you can load them, but they won't work properly). If it isn't, not to worry the gun can be updated (most old Winchesters already have been) or you can use short shells.
Do you intend to load smokeless or black powder? Let's assume that you're going to use smokeless powder, it's much easier to start with. Next you'll need a shot-shell loader. There are many threads devoted to loader selection.
Before you start worrying what components to use, what are you going to do with the gun? With shotguns, it's the use (intended target) that determines the load type. Turkey shooting uses different loads than hunting doves. If you go to the shot-shell manufacturers' web sites you'll get an idea of the broad variety of loads available and their suggested applications.
After you decide what load you want (like a 12-ga, 2 3/4-inch, 1 1/8-oz, 3 dr. eq., #7-1/2 shot, Trap/target load), then get a recipe for that load from one of the many data sources. For the trap load, one recipe, from the Alliant Reloader's Guide is:
• Remington STS Plastic hulls
• Remington 209P primers
• Alliant Clay Dot powder, 18.6-gr
• Winchester WAA12 wads or equivalent
This is just one of many recipes that will work for the example load. With shot-shell loading it's not a mix-n-match situation. You must use the recipes exactly as they are shown in the guides.
You may want to reverse engineer your loads based on component costs. Determine which components are the cheapest and then find a recipe for the load you want using those components. With shot-shell loading the most expensive component is the shot. For economy (and reduced recoil), many shooters reduce their 12-ga loads to 1-oz or 7/8-oz. There are many recipes for reduced loads.
Good luck
Edit:
Oops… I just noticed the reference to SASS, do they not have shot-shell load guidelines?